Mid-Week Freezing Rain Risk Threatens Southern Ontario After Last Weekend’s Devastating Ice Storm
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With recovery efforts well underway across Central Ontario following the devastating ice storm last weekend—which left hundreds of thousands without power—a new weather threat is now on the horizon, potentially hindering progress.
A dynamic and complex system is expected to move into Southern Ontario starting Wednesday morning and continuing into Thursday, bringing with it a mix of impactful weather, including heavy snow, freezing rain, and even the risk of severe thunderstorms.
Unlike the recent ice storm, which brought over 30 hours of relentless freezing rain, this upcoming round will be more typical in nature. Most regions affected can expect four to eight hours of freezing rain, followed by a gradual transition to regular rain as temperatures rise.
While the severity won't match the last event, this system is still expected to bring 5 to 10mm of ice accretion in some of the hardest-hit zones, especially across higher elevations northwest of the Greater Toronto Area, including parts of the Dundalk Highlands and the Kitchener-Waterloo region.
That amount of ice is enough to snap tree branches and potentially cause power outages, especially with infrastructure already weakened. Thankfully, we don’t expect widespread or prolonged outages this time, and restoration efforts should be more manageable. However, with hydro crews still stretched thin from the last storm, even minor outages could take longer than usual to resolve.
Further north, across Central and Eastern Ontario, freezing rain is also expected—though it will be mixed at times with ice pellets and snow. These regions should see a faster changeover to rain, which will help limit overall ice build-up. Still, light icing and slick roads are possible through the afternoon and evening hours, particularly on untreated surfaces.
Adding to the concern are strong wind gusts, which are expected to develop Wednesday afternoon and could return overnight. Gusts may reach 70 to 90 km/h, especially in exposed areas of Central Ontario and regions east of Lake Huron. With already-compromised infrastructure, even moderate gusts could bring additional tree and power line damage.
PRECIPITATION TYPE - MAP FROM WEATHERBELL
Precipitation will begin spreading into Southwestern Ontario late Wednesday morning into the early afternoon. For areas in Deep Southwestern Ontario and along the Lake Erie shoreline, including Windsor, Chatham, and Sarnia, the precipitation will fall as rain from the start, limiting any freezing rain risk.
However, higher elevation zones—particularly those east of Lake Huron and extending through Kitchener, Guelph, and Orangeville—will be dealing with below-freezing surface temperatures trapped under a layer of warm air aloft. This setup is classic for freezing rain, as the rain freezes on contact with cold ground surfaces.
The Greater Toronto Area could see some brief periods of freezing rain as well, particularly in areas away from the immediate lakeshore where it tends to stay cooler. However, any icing here is expected to be minor and short-lived, quickly melting as temperatures rise above freezing.
By mid-afternoon, Central Ontario, especially areas surrounding Lake Simcoe, will likely start off with a wintry mix of wet snow and ice pellets as the first bands of precipitation arrive. These areas could then transition to a few hours of freezing rain before warming into plain rain overnight.
ESTIMATED WIND GUSTS- MAP FROM WEATHERBELL
As the afternoon progresses, wind gusts will begin to increase, particularly in regions east of Lake Huron and into parts of Central Ontario. While model guidance varies, most are pointing to a window of potentially damaging gusts between 70 to 90 km/h.
The NAM model continues to show gusts near 100 km/h, though this may be on the higher end of the spectrum. Overnight, another round of strong gusts is possible as a line of thunderstorms develops. If these storms materialize, localized wind gusts could reach similar or even stronger levels. The severe weather threat should remain confined to Deep Southwestern Ontario.
PRECIPITATION TYPE - MAP FROM WEATHERBELL
As we head into Wednesday evening, freezing rain will come to an end for much of the GTA as temperatures rise above the freezing mark. However, it is expected to persist longer across areas to the northwest, where colder air hangs on longer. This is where the most prolonged and severe icing is likely.
The freezing rain will also spread into parts of Central Ontario and the Bruce Peninsula, both of which were hit hard by the weekend storm and remain vulnerable to additional impacts.
Eastern Ontario will begin to see precipitation late in the day, starting with a burst of heavy snow, followed by a changeover to ice pellets and then freezing rain. How quickly this transition happens will determine how much snow is able to accumulate.
Some model scenarios suggest snowfall totals of 5 to 10 cm are possible, particularly in regions along the Quebec border including Ottawa.
PRECIPITATION TYPE - MAP FROM WEATHERBELL
By around midnight, temperatures will begin to climb across regions southwest of Lake Simcoe, triggering a changeover to rain. Overnight, heavy rainfall will continue to spread across Southwestern Ontario and into the Golden Horseshoe. This rain may come down heavily at times, especially in areas that see embedded thunderstorms.
There is also a risk of severe thunderstorms through the evening and overnight hours in Deep Southwestern Ontario, including Windsor, Chatham, and Sarnia. These storms could produce wind gusts up to 100 km/h, and while the overall tornado risk is low, it can’t be ruled out. A more detailed thunderstorm forecast will be issued on Wednesday if conditions continue to trend toward severe potential.
The freezing rain will gradually lift northward into the Sudbury–North Bay–Ottawa corridor overnight. While these areas may deal with a few hours of freezing rain early on, a transition to rain is expected before daybreak on Thursday.
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The worst freezing rain impacts are expected across higher elevations of Southwestern Ontario and areas northwest of the GTA, where the freezing rain will last longest.
Some of these zones could see 5 to 10mm of ice accretion, and locally higher amounts over 10mm aren’t out of the question depending on exact temperatures and dynamics.
This kind of ice build-up can cause significant surface glazing and may lead to tree and power line damage. Areas most at risk include Listowel, Kitchener, Fergus, Guelph, Orangeville, Shelburne, and parts of York Region.
Northern parts of the GTA could see 2 to 5mm of ice, while areas closer to the lake should remain below 2mm, with ice melting quickly once temperatures rise.
Across Central Ontario and into the Ottawa region, a general 2 to 5mm of icing is expected, though this could trend higher if ice pellets are less dominant or the switch to rain is delayed.
RAINFALL ACCUMULATION - MAP FROM WEATHERBELL
Beyond the freezing rain, this system is also expected to deliver significant rainfall totals. Much of Southern Ontario could see 30 to 50mm of rain, with localized amounts up to 75mm possible in areas affected by thunderstorms.
With local waterways already running high due to spring runoff, this amount of rain could lead to flooding in low-lying areas, particularly where ice and debris continue to block drainage routes. This is of particular concern for communities still without power from the ice storm, as their ability to respond to flooding may be limited.
