May 26, 2025

Slight Risk for Severe Thunderstorms on Monday as a Cold Front Advances Through Alberta

May 26, 2025/ Alannah Campbell

***NOTE: YOU CAN CLICK ON THE MAP TO OPEN A ZOOMABLE IMAGE***

The past week was fairly quiet, as far as active weather is concerned, with the odd pop-up thunderstorm surpassing the severe threshold and a couple of funnel cloud reports. This week, however, is slated to start off with a bang as a cold front will move into Alberta later this afternoon, stretching the length of the province and triggering the development of thunderstorms over a widespread area.

We’ve already seen some scattered showers across parts of Central and Northern Alberta today, but the severe threat won’t begin until this afternoon, around 2-4pm. These will be fast-moving storms that will quickly develop and organize into a north-south line along the cold front as it crosses the province through the afternoon and evening. Storm activity will rapidly diminish as we get later into the evening, but isolated storms could continue until closer to midnight, if conditions remain favourable.

The greatest thunderstorm risk will stretch from Calgary northward up to Fort McMurray, highlighted in yellow on our map. This large region could see damaging wind gusts of up to 100km/h and large nickel to quarter-sized hail, along with torrential downpours. At this point, the threat of a tornado appears to be unlikely, but it can not be completely ruled out.

***Fire danger map for may 26th produced by the government of Alberta***

The amount of lightning associated with today’s storms could also be a concern. Warmer temperatures and drier conditions have elevated the wildfire risk over the past week and has led to High to Extreme Wildfire Danger across the entire province. Significant amounts of lightning, despite the presence of precipitation, could easily spark additional fires given these conditions.

May 15, 2025

Nocturnal Thunderstorm Threat With Damaging Wind Gusts and Isolated Tornado Risk for Southwestern Ontario Tonight

May 15, 2025/ Brennen Perry

updated map - 10:50 PM (CLICK HERE FOR THE PREVIOUS MAP)
***NOTE: YOU CAN CLICK ON THE MAP TO OPEN A ZOOMABLE IMAGE***

UPDATE (10:50 PM):

We’ve been closely tracking the line of storms developing across Michigan, and it’s now set to move into Deep Southwestern Ontario over the next few hours.

Based on the latest model data, current environmental conditions, and how well the storm is holding together despite the lack of daylight heating, we believe there’s enough evidence to upgrade parts of Deep Southwestern Ontario to a ‘strong’ (3/5) risk—mainly due to the potential for intense wind gusts.

Large hail up to the size of toonies is also possible, and we can’t completely rule out an isolated tornado.

We’ve also extended the ‘slight’ (2/5) risk further inland to include areas like Goderich and London, as new data suggests the line could stay fairly strong as it tracks deeper into Southwestern Ontario during the pre-dawn hours. Again, damaging wind gusts remain the primary threat.

The line is expected to cross the border just after midnight, with the severe threat gradually tapering off but still continuing until around 3–4 AM.

ORIGINAL FORECAST

While storm season has had a quiet start in Southern Ontario, things are beginning to ramp up with a late-night storm risk expected between Thursday evening and early Friday morning. A strong line of storms is forecast to form across Michigan late tonight, initially beginning as discrete supercells over parts of Wisconsin and Illinois.

Based on the latest guidance, these storms are expected to organize into a more linear structure as they track eastward, eventually crossing into Southwestern Ontario sometime just after midnight. While they’ll likely lose some of their strength after dark, especially without daytime heating, the atmosphere may still be supportive enough for them to maintain some intensity as they move into our region.

That said, there’s still a fair amount of uncertainty about just how strong this line will be once it crosses the border, and how quickly it might weaken as it tracks northeast through the early morning hours of Friday.

The biggest concern with this system is the potential for damaging wind gusts. This squall line will stretch from the Upper Peninsula of Michigan all the way down through Ohio as it enters Ontario, which could lead to widespread impacts. Areas from the Bruce Peninsula all the way down to Deep Southwestern Ontario are at risk of strong winds embedded within the line.

The highest risk appears to be in Deep Southwestern Ontario, where the line will first cross into Ontario. Regions like Windsor, Leamington, Chatham, and Sarnia are most likely to experience the strongest part of this line. While damaging wind gusts are the main hazard, we also can’t completely rule out the chance for hail and even a brief tornado, especially if the storms arrive a bit earlier than forecast.

Hail up to the size of quarters is possible, and while the tornado risk is considered low overall, it does exist. The biggest concern here is that this is a nocturnal threat. If a tornado were to develop overnight, it would be harder to spot and could be rain-wrapped, making it even more dangerous. That’s why it’s so important to stay alert and have a way to receive warnings while you sleep.

**SIMULATED RADAR** - MAP FROM WEATHERBELL

Storm development will begin with discrete cells over Wisconsin and Illinois, likely forming into a long line around 8–10 PM near Chicago and across Lake Michigan.

The timing of this formation is crucial. If the line develops sooner and sweeps across Michigan quickly, it could result in a more robust severe risk for Deep Southwestern Ontario, where the environment is more favourable before midnight.

No matter the timing, damaging winds remain the most likely outcome with this type of linear storm setup.

As of now, future radar models suggest the storms will cross into Ontario between 1 and 2 AM, hitting areas like Windsor and Sarnia first before stretching further northeast. However, there’s still wiggle room in this timing. It could arrive earlier and stronger, or later and already weakening before reaching our region.

**ESTIMATED TORNADO ENVIRONMENT** - MAP FROM WEATHERBELL

While widespread wind damage is the primary concern tonight, there is some minor tornado potential—especially in Essex County just after midnight. Again, the odds are low, but not zero.

Because of the overnight timing, it's extra important to have notifications enabled on your phone or weather radio. Make sure you have a way to receive alerts while you're asleep in case a warning is issued. Our free app is a great way to instantly get Environment Canada alerts, along with our custom notifications issued for your exact location.

The line of storms is expected to continue northeast through the early morning hours, bringing heavy rain, gusty winds, and frequent lightning to much of Southwestern Ontario and parts of the Greater Toronto Area between 3 and 6 AM.

While the line should gradually weaken during this time, it could still pack a punch in some localized areas. There’s some uncertainty around how long it will be able to hold its strength since the atmospheric environment in Ontario is notably weaker than what the storms had access to in the U.S.

Latest model runs show the system likely fizzles out once it reaches Lake Simcoe, meaning Eastern and Central Ontario probably won’t see much beyond a few scattered morning showers or storms.

Another round of storms is possible Friday afternoon and evening, particularly for Eastern Ontario and parts of Deep Southwestern Ontario. We’ll have more details on that in a separate update.

As it stands, the highest storm risk tonight is in Deep Southwestern Ontario, where we currently have a slight risk (2/5) for severe weather. The main hazard is damaging wind gusts between 12 and 6 AM, though isolated tornadoes and hail up to the size of quarters are also possible.

For the rest of Southwestern Ontario and the Golden Horseshoe, the risk is lower—a marginal (1/5) severe threat—with isolated pockets of wind damage being the most likely outcome. There’s also a very low tornado risk along the Lake Huron shoreline as the line initially pushes into the region. Hail up to the size of nickels could accompany some of these storms.

In addition to the overnight threat, a few isolated pop-up storms are possible during the late afternoon and early evening across parts of Grey-Bruce. While these are not expected to be severe, funnel clouds are possible, including a low-end risk of a landspout tornado. See our custom notification for more on the funnel cloud setup.

Stay weather-aware tonight. Keep your devices charged, notifications turned on, and have a plan in place just in case you need to take shelter quickly. We’ll continue to monitor the latest data and provide updates as the situation evolves, including a possible live stream later tonight.

May 12, 2025

First Slight Severe Thunderstorm Risk of the Year for the Prairies Monday Afternoon Through Tuesday Morning

May 12, 2025/ Alannah Campbell

While we saw some severe storms eventually develop in Southeast Saskatchewan and Southwest Manitoba yesterday, the severe threat for today and into the overnight hours is heightened, resulting in our first Slight Risk of the season.

We’ve already seen heavy rain falling in parts of Central and Southern Alberta today, but thunderstorms have begun to develop and will continue as we progress later through the afternoon and into the evening At this point, it’s possible that these storms may become severe, with the main threat being strong wind gusts and heavy rain. The environment today is also conducive for the development of landspout (non-supercell) tornadoes around Calgary and to the east of the city so we will be watching this situation closely.

It’s further east, in Southern and Central Saskatchewan and Manitoba, that we’re seeing the greatest severe thunderstorm threat. Isolated storms are expected to start developing in the early evening, around 5-6pm and possibly a bit sooner in the afternoon, and models are once again suggesting that the environment could be favourable for the development of supercells.

A bit later in the evening, closer to 7-8pm, we could see some additional storm development in Southwest Saskatchewan as a multicellular line. This complex of storms would travel northeastward across the province and move into Central Manitoba in the early morning hours of Tuesday. It’s during these early morning hours that we could also see more isolated storms develop in Southwest Manitoba.

Large hail, damaging winds, and torrential downpours are all concerns with today’s storms. The possibility of tornadoes is low, but the development of one or two can not be completely ruled out.

May 11, 2025

Marginal Risk for Thunderstorms in Southern Saskatchewan and Manitoba Beginning Sunday Evening

May 11, 2025/ Alannah Campbell

With the arrival of the first heat wave of the year to Southern Saskatchewan and Manitoba this weekend, we’re also looking at our first real threat of severe thunderstorms for the season.

Isolated storms are expected to develop along the American border in both Saskatchewan and Manitoba this evening, starting around 5-7pm. The storms will travel northeastward into both provinces throughout the evening and into the overnight hours.

Models are suggesting that the environment could be favourable for the development of supercells, but further analysis puts the development of severe storms in question and storms could remain sub-severe. One particular area of interest for possible severe storm development will be in Southeastern Saskatchewan and through the Westman and Interlake Regions.

If severe storms end up developing this evening, the overall threats are expected to be limited. These storms could produce small hail and strong wind gusts, while the possibility of a tornado is unlikely.

April 28, 2025

First Strong Severe Thunderstorm Risk of the Season in Southern Ontario on Tuesday With Tornadoes Possible

April 28, 2025/ Brennen Perry

After a gruelling winter filled with relentless snow squalls, powerful winter storms, and a major ice storm to top it all off, we are finally shifting gears into more typical spring and summer-like weather across Southern Ontario. But with the warmer air comes the return of severe thunderstorms, something Southwestern Ontario has already gotten a small taste of over the past few weeks.

We have been closely tracking the potential for our first strong severe weather threat of the season on Tuesday. Model guidance has been consistently highlighting the potential for a very active environment, one capable of supporting tornadoes, large hail, and damaging wind gusts. That risk still looks to be on track, although there remains some disagreement between models on exactly where the strongest environment will set up.

At this time, we believe the strongest severe weather risk will focus across parts of Southwestern Ontario, Central Ontario, and into Eastern Ontario. Other areas across Southern Ontario will still carry a marginal to slight risk, meaning a few severe storms could pop up, but the widespread threat will be lower outside the main zone.

Tuesday’s possible storm threats include one or two tornadoes, large hail — potentially up to the size of toonies or even timbits — widespread damaging wind gusts over 90-100 km/h, and heavy rainfall that could cause localized flooding in some spots.

The storm risk will kick off early Tuesday morning as an area of convection moves across the region between 6:00 a.m. and 12:00 p.m. Most of these morning storms should remain non-severe, but we can't rule out a rogue severe cell, especially in setups like this. Where these morning storms track and how quickly they clear out will be important to watch, as leftover clouds or rain could limit how unstable the atmosphere becomes later in the day.

By the early afternoon hours, the environment is expected to rapidly become more favorable for severe weather. Areas along the Lake Huron shoreline will likely be the first to feel the effects, with the risk then spreading into parts of Central Ontario.

Even though we are confident that the setup is capable of producing severe storms, it’s important to stress that storms actually have to form to take advantage of the environment. Not everyone in the higher-risk zone will necessarily see a storm. These will be isolated events, meaning only a small percentage of the region will be directly impacted.

The highest tornado risk will likely occur earlier in the day across Southwestern and Central Ontario, when individual storms (known as discrete supercells) can remain separated and feed off the prime environment around them.

As the afternoon progresses and storms track further eastward, we expect that they will start to merge into more of a line, which would shift the threat more towards damaging winds and heavy rain rather than tornadoes and large hail.

By late afternoon into early evening, the severe weather risk will push eastward into the Golden Horseshoe and Eastern Ontario. The good news is that the risk should wind down quickly after sunset, which occurs around 8:00 p.m.

There could still be some leftover showers or weak storms lingering into the evening, especially across Eastern Ontario, but the threat for damaging weather will rapidly diminish once the sun goes down.

We’ll continue to monitor this setup closely and provide updates as new data becomes available. Stay tuned, and as always, make sure you have a way to receive alerts if storms develop in your area.

Download our free app to instantly get any Environment Canada alerts and our own custom notifications pushed to your phone. We are planning to go live to cover any storms that develop throughout the day on Tuesday. Please subscribe to our YouTube channel here so you can be notified when we go live.

REGIONAL BREAKDOWN

October 05, 2024

Ontario’s Potential Last Severe Thunderstorm Risk of the Year on Sunday to Usher In a Chilly Start This Week

October 05, 2024/ Brennen Perry

Get ready, Ontario! While we've been enjoying a relatively mild start to fall, aside from a few exceptions, a significant change is on the horizon. As we head into the first weekend of October, it looks like Mother Nature is gearing up to bring in more seasonally appropriate weather. But, true to Ontario's reputation, it won’t happen quietly.

The weekend so far has seen relatively calm weather across Southern Ontario, with many areas enjoying pleasant temperatures in the mid to upper teens. This marks a shift from the consistent 20°C-plus days we experienced through much of September. While it's been nice, things are about to take a turn. We’re expecting a sudden surge of warmer air on Sunday, and that warm-up could set the stage for some potentially severe weather as we move into the morning and afternoon hours.

This brief October "heatwave" could push temperatures close to 20-25°C in Deep Southwestern Ontario and across the Golden Horseshoe. For those of you in Central and Eastern Ontario, however, don’t expect to feel much of this warmth. A stubborn pocket of cooler air is going to dig in, holding temperatures in the mid-teens across that region, keeping it much cooler than the rest of the province.

Unfortunately, this warm-up isn’t all sunshine. It will come hand-in-hand with some unsettled weather. A potentially strong line of thunderstorms is expected to cut across Southern Ontario on Sunday morning and afternoon. The latest data suggests that this line of storms could develop over Lake Huron by late morning and track eastward, making its way onshore just east of Lake Huron and Georgian Bay.

**SIMULATED RADAR @ 12 PM ON SUNDAY** - MAP FROM WEATHERBELL

There is still some uncertainty regarding the intensity of these storms. The early timing and limited warm air this far north may impact how severe the storms get. However, the atmosphere seems primed to support at least a marginal severe threat. We could see strong wind gusts, potentially reaching 90 km/h, and even hail up to quarter-size. There’s also a possibility that the risk level could be upgraded to slight by morning if conditions appear more favourable.

There is a low tornado risk—while it can’t be completely ruled out, the messy, linear storm structure might limit the chances of an isolated tornado forming. Still, it’s always better to stay cautious when severe weather is in the forecast.

This line of storms will continue pushing eastward through the Golden Horseshoe and areas east of Lake Simcoe by early to mid-afternoon. There’s potential for some intensification as the day progresses, or we could even see additional storms developing in the wake of the initial line. The zone between Bancroft, Peterborough, and Durham Region, and possibly stretching into Niagara, seems to have the highest risk for severe weather, should the conditions align more favourably.

By the late afternoon, the bulk of the storm activity will shift into the United States, where further severe weather could develop over Upstate New York and Pennsylvania. As a result, the storm threat across Southern Ontario should rapidly diminish by early evening. Given the time of year and the fact that cooler weather is set to follow, it’s quite possible that this could be our last widespread severe weather event of the season.

**ESTIMATED TEMPERATURE @ 7 AM ON TUESDAY** - MAP FROM WEATHERBELL

Speaking of cooler weather, expect a noticeable drop in temperatures as we start the new week. By Monday and Tuesday, much of Southern Ontario will feel the chill, with daytime highs struggling to climb into the mid-teens.

Central and Eastern Ontario could be even cooler, with some areas potentially stuck in single-digit highs. The nights will be even colder. On both Tuesday and Wednesday mornings, some regions in Central and Eastern Ontario could dip below 0°C, bringing a risk of frost for a large portion of Southern Ontario.

At this point, we’re not expecting s-word to enter the forecast this week at least in Southern Ontario, but the cold snap will certainly make it feel like fall has truly arrived. So, if you’ve been holding off on packing away your summer wardrobe, it might be time to start thinking about those cozy sweaters and heavier jackets.

**LONG RANGE TEMPERATURE FORECAST FOR THANKSGIVING SUNDAY - NOTE: THIS WILL LIKELY CHANGE!** (MAP FROM WEATHERBELL)

However, there might be some good news as we look ahead to the Thanksgiving long weekend. Early indications suggest a potential return of warmer air by next weekend, bringing with it another temperature boost. Some models hint at temperatures pushing 20°C once again in parts of Southern Ontario, which would be quite a surprise for Thanksgiving, given that we’ve seen flurries on the holiday in previous years!

It’s still too early to say for sure, though, as the forecast could change over the coming days. But for now, we’ll remain optimistic about the possibility of a pleasant, mild Thanksgiving weekend. As always, we’ll be monitoring the situation closely and will provide a more detailed Thanksgiving preview later this week.

September 25, 2024

Isolated Storms Could Bring Tornado Risk to Central Ontario and GTA on Wednesday

September 25, 2024/ Brennen Perry

As we near the end of what has been a relatively quiet month for weather across Southern Ontario, we’ve been locked in a pattern of calm conditions and unseasonably warm temperatures. But now, as we enter the first week of autumn, a shift is on the horizon!

Rainy weather has returned across much of Southern Ontario over the past few days, and unsettled conditions are expected to continue into Wednesday. There’s also potential for severe weather during the late morning, extending into the afternoon.

RAINFALL WARNING (IN GREEN) ISSUED BY ENVIRONMENT cANADA

We’re already seeing pockets of heavy rain and thunderstorms overnight, which are expected to persist until sunrise. Environment Canada has issued rainfall warnings for some areas, where localized amounts of up to 50 mm are possible.

While it's uncertain, some models indicate a slight tornado risk in the morning, particularly around the Golden Horseshoe and Niagara Region. Though this is unlikely, it’s still worth noting.

The timing of when these overnight storms clear out will be key in determining the risk for later in the morning and afternoon. According to the latest models, most storms should dissipate by sunrise, allowing the atmosphere to become more unstable heading into the late morning.

From around 11 AM through early afternoon, conditions could become favorable for isolated thunderstorms. The strongest setup is expected around Lake Simcoe, extending into the Muskoka and Haliburton regions.

While most storms are expected to remain non-severe, there is a chance of isolated tornadoes, along with marginally severe wind gusts and hail up to the size of quarters.

The Greater Toronto Area and Niagara Region are under a marginal risk for severe weather, primarily due to the potential for an isolated tornado during the afternoon and early evening. This marginal tornado risk also extends into Algonquin Park and parts of southwestern Quebec.

It’s important to keep in mind that this forecast has a high bust potential—some models show little storm development during peak hours of instability. This forecast assumes storms will develop during the afternoon, but we may need to update and downgrade the risk in the morning if it looks less likely that storms will form.

September 17, 2024

Late Season Storms Bring a Slight Severe Risk for Southern Saskatchewan Tuesday Evening and Through Wednesday Morning

September 17, 2024/ Alannah Campbell

As we continue later into September, it seems that summer is still hanging on, with some active weather this morning and into the afternoon and additional stronger severe storms beginning later this evening that will continue into Wednesday morning. The combined wind, hail, and tornado threat from the impending storms has resulted in a Slight Risk for a large portion of Southern Saskatchewan.

The storms will start to develop as individual cells along the border in the early to mid-evening in Southwest Saskatchewan. This will be followed by a line of storms from south of the border that will make their way northward into the province later in the evening and into the overnight hours. A final round of storms is expected to arrive a few hours later, spreading much further north into Central Saskatchewan and weakening later into the morning. Due to the positioning of the low pressure that these storms will the centred around, areas closer to the Alberta border could see steady moderate rainfall lasting throughout Wednesday afternoon and evening.

These storms are expected to produce hail that could be larger than a toonie, along with damaging wind gusts upwards of 100km/h, and the possibility of one or two tornadoes. There is also the concern of localized flooding, particularly further west, where the storms and the subsequent extended period of rainfall could bring up to 100mm of rain.

September 16, 2024

Slight Risk for Severe Thunderstorms in Southern Manitoba This Afternoon and Into Tuesday Morning

September 16, 2024/ Alannah Campbell

Following some morning and early afternoon rain, Southern Manitoba can expect more active weather with severe thunderstorms beginning this afternoon and continuing into Tuesday morning. The possibility of large hail and flooding caused by heavy downpours make this a Slight Risk in Southeast and South-Central Manitoba.

The activity will begin this afternoon with a line of storms pushing northeastward into the region from North Dakota. Development of further storms will continue through the evening and into the pre-dawn hours of Tuesday, resulting in some locations seeing multiple rounds of thunderstorms. The storms that develop later into the evening could be more organized and are expected to be stronger that the afternoon storms.

These storms may bring some large hail, up to the size of a timbit, as well heavy rains that could result in areas of localized flooding. There will be some strong wind gusts that are expected to top out in the 90-100 km/h range and the possibility of an isolated tornado can not be completely ruled out.

August 29, 2024

Stormy Start to Long Weekend in Southern Ontario With Potential Severe Risk on Friday

August 29, 2024/ Brennen Perry

As we kick off the Labour Day long weekend, traditionally seen as the unofficial end of summer in Southern Ontario, we're keeping an eye on the potential for some active weather on Friday.

Friday is likely to be the warmest day of the long weekend, with temperatures soaring into the mid to high 20s during the afternoon, and the humidex making it feel into the 30s. The only exception is Eastern Ontario, where daytime highs will peak in the low to mid 20s.

This warm air will fuel thunderstorms expected to develop later in the afternoon and continue into the evening hours. The main risk zone covers Southwestern Ontario along the Lake Huron shoreline, but parts of the Golden Horseshoe and Central Ontario could also see some severe storms.

Based on the latest model data, instability will increase throughout the afternoon as daytime heating builds energy in the atmosphere. Earlier data suggested that storm development might be delayed until late evening or even overnight, which would significantly reduce the available environment to fuel these storms.

However, the newest model data shows storm development occurring much earlier, as soon as 4-5 PM—right during the prime time when conditions are most favorable. Most models agree on storms developing over Lake Huron in the late afternoon, then moving ashore between Owen Sound and Goderich. Initially, storms are likely to be isolated but could merge into a cluster as they track eastward through Grey and Bruce counties along the southern shoreline of Georgian Bay.

Additional storm development is possible to the southwest around Windsor, Sarnia, Grand Bend, and London, where the environment is actually stronger than in the north. Although there's lower confidence in storm development here, any storms that do form could become quite severe, with all hazards on the table, including a risk of an isolated tornado.

Looking towards the evening, the earlier cluster of storms is expected to reach the Lake Simcoe region by early evening. By this time, the storms will likely have lost some intensity but could still pose a marginal wind damage risk through the northern GTA and parts of Central Ontario, including Simcoe County, Muskoka, and the Kawartha Lakes region.

Storms are likely to linger into the early overnight hours across Southwestern Ontario and the Golden Horseshoe. There are indications of a flooding risk, with storms ‘training’—where multiple storms move over the same area like a train—leading to significant rainfall amounts. It’s unclear exactly where these storms might set up, but if they occur over urban areas that are more prone to flash flooding, significant flooding could occur overnight on Friday.

Currently, we’re going with a ‘slight’ (level 2/5) risk for severe storms in Southwestern Ontario on Friday. This is driven by the potential for fairly widespread damaging wind gusts. Hail up to the size of quarters and an isolated tornado risk are also possible hazards. We may need to introduce a more targeted ‘strong’ (level 3/5) risk zone in an updated forecast if confidence increases in where the storms will develop.

For those in Central Ontario and around the Golden Horseshoe, we’re assigning a ‘marginal’ (level 1/5) risk, mainly due to the potential for 90 km/h wind gusts later in the evening, along with flash flooding from multiple rounds of storms. While the tornado risk isn’t zero, it will be less of a concern by the time the storms reach these areas.

August 26, 2024

Summer’s Last Hurrah as Heat Returns to Southern Ontario & Conditional Strong Severe Threat on Tuesday

August 26, 2024/ Brennen Perry

Ready or not, the end of summer is rapidly approaching, with just one week left before students head back to school. Signs of autumn are already peeking through, with Environment Canada issuing a frost advisory last week in Northern Ontario, and of course, the arrival of pumpkin spice latte season!

However, it seems that Mother Nature has decided to give us one last taste of mid-summer weather. The start of this final week has brought steamy conditions, with warmer air making it feel like the 30s or even low 40s in some areas thanks to the humidex.

Along with the return of hot temperatures, we can expect some active weather, with multiple rounds of thunderstorms likely on Tuesday, possibly extending into Wednesday. While there is some uncertainty regarding the exact strength and timing of these storms, there is a risk that some could reach severe levels, bringing damaging wind gusts, large hail, and the potential for one or two tornadoes.

As mentioned, the dynamics of Tuesday’s storm risk remain highly conditional on timing. Some models suggest that decaying thunderstorm activity from Michigan could track into Southwestern and Central Ontario during the morning hours. If this occurs, it could deplete the atmospheric energy needed for storms later in the day when conditions are more favourable.

It's important to highlight that the potential for a "bust" in this event is moderately high, which is why we're focusing on the overall storm threat based on the environment, should storms develop.

The strongest conditions are expected along the southeastern shoreline of Lake Huron, extending into Deep Southwestern Ontario during the afternoon and evening hours. Storms could begin developing anytime between 12-1 PM and continue until sunset around 8 PM.

There is higher confidence in storm development further northeast around Lake Simcoe and into Central Ontario, though the environment isn't as strong in these areas. Multiple rounds of thunderstorms throughout the afternoon and early evening could impact the North Bay, Muskoka, Parry Sound, and Algonquin Park regions, with flash flooding being the primary concern.

In addition to the daytime storm risk, there are indications of a nocturnal storm risk around midnight, continuing into the pre-dawn hours of Wednesday. A strong line of storms could form over Michigan or Lake Huron and track across Southern Ontario. However, this will depend on earlier storms and how much energy remains in the atmosphere.

Regarding expected storm hazards, we're assigning a 'strong' risk (level 3 out of 5) for parts of Southwestern Ontario, including Windsor, Chatham, Sarnia, Grand Bend, and London, based on the potential for widespread wind damage—again, this is conditional on storm development. Large hail up to the size of toonies and one or two tornadoes are also possible threats.

There is a widespread 'slight' risk for the rest of Southwestern Ontario and into Central Ontario. All storm hazards are possible, including strong wind gusts, large hail, and an isolated tornado. As mentioned, storms in Central Ontario could bring a flash flooding threat, with rainfall totals potentially reaching 100 to 150mm in the hardest-hit locations.

Further east, the Golden Horseshoe and a portion of Eastern Ontario are under a 'marginal' risk, where some storms later in the day or overnight could approach severe limits, primarily due to strong wind gusts and hail up to the size of quarters.

August 25, 2024

Threat of Massive Hail is the Driving Force Behind a Widespread Strong Severe Risk in Southeast Manitoba Sunday Afternoon IF Storms Develop

August 25, 2024/ Alannah Campbell

It’s been a very active few days across the Prairies and this morning was no exception, with destructive wind gusts pummelling parts of East Central Saskatchewan and the Westman and Parkland Regions.

Unfortunately, this trend of dangerous severe weather will likely continue this afternoon, but this time the target will be Southeastern Manitoba. The possibility for massive hail across the region has resulted in this being a widespread Strong Risk for severe thunderstorms for this afternoon.

Once again, weather models are struggling with pinpointing these storms, but the ingredients for severe weather should all be in place and there is a potential for severe storm development, which warrants a forecast. Today will be an “IF day” in the sense that IF storms end up developing, they are expected to be very strong and widespread across the region. With the intense heat and temperatures feeling into the low 40s, along with ample moisture and instability, the environment will be primed for storms, but a strong enough trigger will be necessary for them to occur.

This storm development could begin early this afternoon, as the existing line of storms pushes northeastward through the Interlake Region. Behind this, additional storms could develop along a cold front and make their way eastward through the Red River Valley and Interlake Region during the afternoon and the Eastman and North Eastman Regions in the evening and overnight hours. Whether or not this development actually occurs is still uncertain.

If the severe thunderstorms end up developing this afternoon, the major threat will be very large hail. Golf ball-sized hail appears to be likely with these potential storms, with even up to tennis ball-size possible. Widespread damaging wind gusts over 100km/h would also be associated with these storms, as well as up to 100mm of rain resulting in localized flooding and the possibility of a tornado.

This could very well end up being a bust, but the threats involved in the event that storms do develop are quite significant and it’s important to be prepared.

August 24, 2024

Strong Risk for Severe Thunderstorms in Southeast Saskatchewan This Evening and Through Sunday Morning

August 24, 2024/ Alannah Campbell

Southeastern Saskatchewan is in the crosshairs for severe weather once again, with some storms firing up along the American border later this evening followed by another round of strong storms early Sunday morning. The hail, wind, and tornado risk between the evening and morning storms makes this a Strong Risk along the southern border and a Slight Risk stretching through Southeast Saskatchewan and into East Central Saskatchewan.

The activity will begin this evening with the development of supercell storms along the Montana border that will push northeastward through the late evening. These storms could be quite strong and will be followed by even more development from south of the border after midnight. This second round is expected to be more organized and bringing more widespread impacts as they follow the northeastward trend across Southeastern Saskatchewan through the morning.

These storms could be quite impactful with very large hail that will likely be golf ball-sized, possibly even larger, and widespread damaging wind gusts upwards of 120km/h, as well as one or two tornadoes. There is also the concern of localized flooding with heavy downpours that could bring up to 100mm of rain.

August 24, 2024

Greatest Severe Thunderstorm Threat for Saturday Afternoon Shifted West; Still Slight Risk for Southern Manitoba

August 24, 2024/ Alannah Campbell

Following this morning’s thunderstorms, we are still expecting more severe weather for Southern Manitoba later today, however the anticipated strength of those storms has diminished and the area they’re expected to hit has also changed. The strongest storms of the day are now expected in Southern Saskatchewan, but the potential for damaging winds, large hail. and localized flooding still result in a Slight Risk for severe thunderstorms in the Westman, Parkland and Northern Interlake Regions.

The exact timing of these storms is tricky to establish due to uncertainty between weather models, leaving three possible scenarios.

Scenario 1

Large storms could begin to develop in the mid-afternoon just east of the Saskatchewan border in the Parkland Region as isolated supercells which would travel northeastward across the province. Development of additional storms would continue through the evening and early overnight, following the same northeastward trajectory. These storms would then be followed by a more organized cluster of storms crossing through the region Sunday morning.

Scenario 2

Smaller storms could start to develop in the Parkland Region in the mid to late afternoon and quickly become more organized into a strong line that spreads into the Northern Interlake and travels southeastward through the evening before starting to fall apart approaching the Central Plains overnight. In this scenario, the storms Sunday morning would be weak, if they occur at all.

Scenario 3

A handful of small storms could pop-up starting in the later in the afternoon, once again in the Parkland Region, and continuing into the late evening, but not amount to anything too concerning. Then, in the early morning hours, a large cluster of storms could push northeastward into the region from Saskatchewan, followed by a second round of strong storms later in the morning.

Regardless of which of the three scenarios unfolds, it is likely that there will be strong storms in Manitoba over the next 24 hours. The threats from these storms will be the large hail, with up to toonie-size likely and damaging wind gusts that could exceed 100km/h, as well as one or two tornadoes . There is also the concern of localized flooding because these storms are expected to occur over the same area. It’s important to note that the level of uncertainty between weather models means that this could very well end up being a classic “bust” day, but we believe that it is better to be prepared in the event that any one of these scenarios materializes.

August 23, 2024

Slight and Strong Risk for Severe Thunderstorms Across Southern Manitoba Saturday, Hitting in Multiple Rounds

August 23, 2024/ Alannah Campbell

It will be a hot day across Southern Manitoba on Saturday, but there will be some active weather, in the form of a line of severe thunderstorms, to contend with before the temperatures start to climb. More storms will hit the region later in the day, but the timing remains a little unclear. Regardless, the risk of large hail and damaging wind gusts, along with the possibility of a tornado makes this a Strong Risk for severe thunderstorms in Southwestern Manitoba, including Brandon, and a Slight Risk across much of the rest of Southern Manitoba.

The first line of storms will make their way into Southwestern Manitoba around sunrise Saturday morning, packing a punch with strong winds and large hail. These storms will lose steam as they travel eastward across the width of the province throughout the morning and into the early afternoon. Following this line of storms, it will be a hot day across the region, feeling closer to 40°C with the humidity, which should provide ample fuel for another wave of storms. The exact timing of this second line of storms is still uncertain. Some models are suggesting that the additional storms could start Saturday evening and make their way across Southern Manitoba overnight and into Sunday morning. On the other hand, there are other models that show the second line of storms developing in the early morning hours of Sunday and continuing into the early afternoon, followed by a third line of storms beginning Sunday evening. Due to this uncertainty, we will likely have a revised forecast for the secondary storm development posted Saturday afternoon.

The threats from these storms will be the large hail, with up to golf ball-size possible, as well as widespread damaging wind gusts that could exceed 100km/h and approach 120km/h, along with the possibility of a tornado or two touching down. There will also be a flooding risk, with these storms expected to bring up to 100mm, particularly to areas that will experience multiple rounds of storms.

August 23, 2024

UPDATE: Slight Risk for Severe Thunderstorms for Friday Now Extends into Calgary

August 23, 2024/ Alannah Campbell

In an update to the forecast that was posted yesterday evening, we have extended the boundaries of the Slight Risk region to include Calgary and the entire Highway 2 corridor south of the city. The combination of damaging wind gusts, large hail, and the possibility of an isolated tornado from today’s has resulted in the Slight Risk for this area, along with Lethbridge, Medicine Hat, and Drumheller.

Thunderstorms have already begun to develop in Montana, moving northward towards the border. They will start to cross into Alberta later this afternoon and early evening, spreading across Southern Alberta throughout the rest of the evening and overnight. It’s possible that the storms could become organized into a line that will push northeastward starting later in the evening which will impact a more widespread area than just isolated storms.

The main threat from these storms will be the hail, with up to toonie to timbit-size likely, as well as damaging wind gusts that could exceed 100km/h and even approach 130km/h. At this time, there does not appear to be too much of a flooding risk, with these storms expected to bring less than 50mm of rain over the span of a few hours. An isolated tornado can also not be completely ruled out.

August 22, 2024

Slight Risk for Severe Storms in Southern Alberta to Finish the Week; Forecast Could be Upgraded

August 22, 2024/ Alannah Campbell

Friday will be another hot day across Southern Alberta and along with that heat comes severe thunderstorms. A combination of damaging wind gusts, large hail, and the possibility of an isolated tornado means that there will be a Slight Risk in an area that includes Lethbridge, Medicine Hat and north towards Drumheller.

The storms will cross into Alberta from Montana in the south starting in the late afternoon and early evening, spreading across the region throughout the evening and overnight hours. It’s possible that the storms could become organized into a line that will push northeastward starting later in the evening that will impact a more widespread area than just isolated storms.

The main threat from these storms will be the hail, with up to toonie-size likely, as well as damaging wind gusts that could exceed 100km/h. At this time, there does not appear to be too much of a flooding risk, with these storms expected to bring less than 50mm of rain over the span of a few hours. An isolated tornado can also not be completely ruled out. The risk level could change with more data from short-range models so stay tuned for any updates to this forecast.

August 21, 2024

UPDATE: Isolated Strong Risk for Severe Storms in Southern Saskatchewan Beginning Wednesday Evening

August 21, 2024/ Alannah Campbell

It will be another stormy day in Southern Saskatchewan on Wednesday, with active weather beginning later in the day and continuing through to Thursday morning. A combination of very large hail, damaging wind gusts and the possibility of tornadoes has led to us upgrading this forecast to a Strong risk, surrounded by a Slight Risk in the Southeastern region of the province.

The storms are anticipated to start in the early evening Wednesday in the southwest as some isolated cells. These individual storms will quickly merge and become large clusters of storms that will move northeastward across Southern Saskatchewan throughout the rest of the evening and into the early morning hours of Thursday. The storms will become more organized as they move across the province, as well as becoming more intense, thus increasing the threat from Marginal, Slight and in an isolated area that includes Regina, a Strong risk.

The main threat from these storms will be the hail, with toonie to timbit size with isolated hail up to golf ball size, as well as damaging wind gusts that could exceed 100km/h. Heavy downpours will be associated with these storms and some areas, particularly in Southeast Saskatchewan, could see over 50mm of rainfall. There is also the risk of these storms producing one or two tornadoes so be sure to keep an eye out for watches and warning being issued by Environment Canada later in the day.

August 16, 2024

Wet & Unsettled Weekend Brings Threat of Severe Storms and Significant Rainfall to Southern Ontario

August 16, 2024/ Brennen Perry

As we approach the final weeks of summer, with the back-to-school season around the corner and the arrival of astronomical autumn just under a month away, it seems Mother Nature is continuing the trend of a wet summer. The upcoming weekend is set to bring multiple rounds of rainy weather, and by early next week, we might even get a taste of early fall-like conditions, with possible single-digit lows for parts of Southern Ontario.

Rain over the next few days will come in waves, starting Friday afternoon in Southwestern Ontario and lingering through the weekend. Thunderstorm activity will play a significant role in this weekend’s rainfall, potentially leading to localized totals approaching 80mm. The rain should taper off by early Monday, with Eastern Ontario seeing the last of the precipitation.

As of Friday afternoon, the first wave of rain is already moving into Southwestern Ontario, extending into regions around Lake Huron and Georgian Bay. This cluster of rain and embedded thunderstorms is expected to gradually track eastward into the Golden Horseshoe and Central Ontario by Friday evening.

Rainfall amounts will be highly variable due to the thunderstorm component, but widespread totals of 5-15mm are expected by Saturday morning. Localized amounts could reach 25-50mm for areas that experience thunderstorm activity, though it’s difficult to pinpoint exactly where this will occur.

Moving into Saturday, the rain will become less widespread, with a focus on Eastern Ontario and Southwestern Ontario during the morning hours. Eastern Ontario is expected to see lingering precipitation from Friday night’s first wave of rain.

We are also closely monitoring the risk of pop-up thunderstorms in Southwestern Ontario, extending into the Golden Horseshoe through late morning and early afternoon on Saturday. While these storms are expected to be mostly non-severe and primarily a rainfall risk, we can’t rule out a marginal severe threat, as the environment could potentially support some hazards, including hail and damaging wind gusts. An isolated tornado can’t be ruled out, though the risk is relatively low.

More isolated pop-up thunderstorms are expected across Southwestern Ontario, the Golden Horseshoe, and Central Ontario throughout Saturday afternoon and evening. There is concern that these storms will be slow-moving, with some areas experiencing multiple rounds of storms in a short time frame. This could lead to a heightened flash flooding risk, particularly in more urban parts of Southern Ontario, such as the Greater Toronto Area.

Due to the localized nature of the rain on Saturday, some areas may not see a drop, while others could receive upwards of 50-75mm of rain. The heaviest rain appears to be concentrated along the Hwy 401 corridor between London and Toronto, with other pockets of heavy rain in Central Ontario. However, this is just a general idea from one model and could shift depending on where the storms develop.

There should be a break in the rainfall overnight Saturday for most areas, although a few localized showers are possible, particularly around Southwestern Ontario and the Golden Horseshoe.

Similar to Saturday, pop-up thunderstorms are expected to return across Southern Ontario on Sunday morning and continue throughout the afternoon. These storms could bring additional heavy rainfall to the same regions affected by Saturday’s storms. Again, actual rainfall totals will vary significantly depending on where the storms hit, but some areas could see another 25-50mm (or more) by the end of Sunday.

We are also closely monitoring the risk of severe storms in Eastern Ontario later in the afternoon and early evening on Sunday. Storms that develop here could bring damaging wind gusts, large hail, and potentially an isolated tornado. It’s still two days away, so much can change, but it appears that the Ottawa Valley, extending along the international border in Eastern Ontario, could see some marginally severe storms.

Rain is expected to continue overnight into Monday morning for Central and Eastern Ontario, with pockets of heavy rain and embedded thunderstorms. Southwestern Ontario and the Golden Horseshoe should finally see the rain taper off by late Sunday evening, with the rain ending in Eastern Ontario sometime Monday morning. This will give way to clear conditions for Monday afternoon and evening.

However, the calm weather will bring much colder air, with overnight temperatures plummeting into the single digits across much of Southern Ontario on Monday and Tuesday nights. Daytime highs will struggle to reach the 20°C mark on Tuesday and Wednesday, making for a much cooler week compared to what we’ve experienced this summer.

August 13, 2024

Slight Risk for Severe Storms in Southern Saskatchewan for Tuesday into Wednesday

August 13, 2024/ Alannah Campbell

In a repeat of Monday, storms will be likely in Saskatchewan again Tuesday and continuing into early Wednesday. This time, however, the threat has increased to a slight risk across a large swath of Southern Saskatchewan which could see as much as 100mm of rain, the occasional wind gust exceeding 90km/h, up to toonie-size hail and the possibility of an isolated tornado.

The initial storm activity is anticipated to start mid-afternoon Tuesday in the west with some isolated cells, but things will begin to ramp up as we approach the evening hours. This is when we expect these individual storm cells to begin to merge, creating clusters of storms that will push eastward across the southern half of the province throughout the evening and overnight and into the early morning hours of Wednesday.

The main threat from these storms will be the hail, with up to toonie-size likely, as well as wind gusts that could reach 100km/h. There is also the possibility of training thunderstorms, multiple storms that follow the same track, so flooding will be a concern as some areas could see up to 100mm of rain in only a few hours. It seems unlikely based on the data, but an isolated tornado can not be completely ruled out.

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