Northern Ontario: Fall Weather Hazards Outlook for Sunday, October 10, 2021

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Forecast Discussion

Heavy rain will work its way through parts of Northwestern Ontario with the heaviest totals found along the Internation border and the northwestern Lake Superior shoreline including Thunder Bay. Rainfall totals by the end of Sunday in this area are expected to range from 25-40mm with localized pockets picking up close to 50mm.

In addition to the rain, heavy fog will yet again be an issue overnight and into Sunday morning for much of the Lake Superior shoreline. If you’re travelling out on the roads before sunrise then be sure to drive cautiously as the fog can result in near-zero visibility. The fog will come to an end by the late morning hours after sunrise.

Northern Ontario: Fall Weather Hazards Outlook for Saturday, October 9, 2021

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Forecast Discussion

Heavy fog patches are expected to develop around Lake Superior during the early morning hours on Saturday. This could result in poor driving conditions due to near-zero visibility. Be sure to drive with caution. The fog will dissipate just after sunrise.

Southern Ontario: Fall Weather Hazards Outlook for Saturday, October 9, 2021

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Forecast Discussion

Heavy fog is possible throughout parts of Southwestern Ontario including Windsor, Sarnia, London and K/W during the early morning on Saturday. This may reduce visibility on the roads to near-zero before sunrise so be sure to travel with caution. As usual, the fog will burn off quickly after sunrise. Heavy rain is also expected during the day on Saturday with the heaviest rainfall accumulation around Lake Huron and Georgian Bay. Although with the highest rainfall totals topping out at around 10-15mm, it won’t come close to the 25mm threshold to include on the outlook map.

Northern Ontario: Fall Weather Hazards Outlook for Friday, October 8, 2021

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Forecast Discussion

Heavy fog is expected to develop around Lake Superior and into parts of Northeastern Ontario during the overnight and into Friday morning. This could cause reduced visibility on the roads and make for difficult travel conditions. The fog will dissipate after sunrise.

Southern Ontario: Fall Weather Hazards Outlook for Friday, October 8, 2021

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Forecast Discussion

Heavy fog has developed around the Hamilton/Niagara region this evening and is expected to further expand to encompass parts of Southwestern Ontario overnight and into Friday morning. Fog is also possible throughout Eastern Ontario during the early morning hours on Friday. This could cause reduced visibility on the roads and make for difficult travel conditions. The fog will dissipate after sunrise.

Soaking Start To Fall Across Southern Ontario With Up to 75–125mm of Rainfall Accumulation by Thursday

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The calendar might show the start of fall as of Wednesday afternoon, but it will seem like Mother Nature has mistaken it for the start of spring with expected significant rainfall across the region over the next few days. This rainfall event will get going late Tuesday evening as bands of heavy rainfall and embedded non-severe thunderstorms set up from Extreme Southwestern Ontario and into parts of Central Ontario. It will continue overnight and throughout the day on Wednesday encompassing almost the entire region.

The rainfall will come in waves on Wednesday with isolated heavier pockets where embedded thunderstorms could deliver locally heavier rainfall amounts. There might be a few hours of clearing during the afternoon on Wednesday particularly around the Golden Horseshoe, but it won’t last long as more rounds of heavy rainfall move into the region from south of the border. This round will linger past the evening and overnight for the second night of heavy rainfall with a focus on Central Ontario and the GTA.

We will also see some strong wind gusts developing along the Lake Huron and Georgian Bay shoreline during the evening on Wednesday and continuing overnight. Wind gusts of between 50-80km/h are possible especially in areas close to the shoreline, but they shouldn’t reach severe levels.

By early Thursday, we’ll finally see the light at the end of the tunnel as the flow of heavy rainfall slowly breaks apart in the west and shifts to the east. Central and Southwestern Ontario should see the rain taper off by the late morning or early afternoon. Rain will continue for Eastern Ontario through the day on Thursday and into the overnight hours but it will be less intense than what we saw the previous night. The system will fully exit Southern Ontario by Friday morning although it will be short-lived with more rainfall possible over the weekend.

In terms of accumulation, we expect the heaviest rainfall totals will be found in a zone extending from Windsor, through regions east of Lake Huron and into portions of Central Ontario including Muskoka and Algonquin Park. Totals here will generally range from 75-125mm with isolated pockets that see thunderstorm activity picking up over 125mm. The rest of Southern Ontario except for Northeastern and Eastern Ontario will see widespread amounts between 40-75mm with locally up to 100mm. Eastern Ontario should see around 25-50mm, but most of that rainfall will come on Thursday instead of the first two days.

It’s important to note that this rainfall won’t be coming all at once as it will be spread out over the next 72 hours. Flooding will still be a major concern with this event, but it won’t be anywhere close to the impacts if we saw the same amount of rain from a stationary thunderstorm in just a few hours. Most of the rainfall will come on Wednesday and into early Thursday morning except for Eastern Ontario which will mostly stay dry until late Wednesday and Thursday.

Southern Ontario: Thunderstorm Outlook for Tuesday, September 21, 2021

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Forecast Discussion

Heavy rainfall late in the day on Tuesday will move into parts of Southern Ontario mainly along the Lake Huron and Georgian Bay shorelines. There is the potential a few embedded thunderstorms may be present within this area of rainfall, but it’s very questionable. Due to the lack of intensity and coverage, we won’t issue an outlook for this risk.

Northern Ontario: Thunderstorm Outlook for Monday, September 20, 2021

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Forecast Discussion

Heavy rainfall will continue to affect Northwestern Ontario throughout the day on Monday. This area of rainfall will also have some embedded thunderstorm activity which should mainly remain non-severe with strong wind gusts and heavy rainfall as the main threats. The thunderstorm activity will slowly track to the east during the day and could also bring some thunderstorms to parts of Northeastern Ontario overnight into Tuesday - more details on this soon.