Thunderstorm warnings, watches in effect for parts of GTA as dangerous weather threat peaks Wednesday
Parts of the GTA are under yellow‑level severe thunderstorm warning or watch, as forecasters track a volatile and fast‑evolving weather system expected to bring multiple rounds of dangerous storms, torrential rainfall, damaging winds, large hail and the risk of an isolated tornado throughout Wednesday. Environment and Climate Change Canada (ECCC) expanded its warning area early […]
The Greater Toronto Area is experiencing heightened severe thunderstorm warnings and watches on Wednesday, as forecasters monitor a rapidly changing weather system. Environment Canada has expanded its warning zone this morning to include Toronto, Mississauga-Brampton, Burlington-Oakville, Hamilton, Halton Hills-Milton, and Pickering-Oshawa/Southern Durham Region, among other areas.
Heavy rain may trigger flash flooding and significantly reduce visibility. Large hail poses risks of injury and considerable damage. A previous yellow-level severe thunderstorm warning for Toronto and the GTA was lifted just before 7 a.m. Wednesday.
The weather pattern follows a hot day in Toronto, with humidex values nearing 40. Early Wednesday, a line of severe thunderstorms moved east at 50 km/h, causing strong wind gusts, quarter-sized hail, and heavy rain in communities such as Markham, Pickering, Ajax, Whitby, Oshawa, Newmarket, and Lindsay. Toronto is set to face foggy, slow, and hazardous morning commutes, with visibility dropping below a kilometre and 30-50 mm of rain possible within an hour.
The TRCA warns that watersheds are already saturated after 8 to 55 mm of rain fell on Tuesday, making any further heavy downpours likely to cause flash flooding, rapidly rising water levels, and perilous river conditions. From the afternoon into the evening on Wednesday, the highest risk for severe weather will arise from a second, more powerful wave of thunderstorms.
This round is forecasted to bring up to 50 mm of rain, with potential for damaging wind gusts of 110-130 km/h, hail 3-5 cm in diameter, isolated tornado potential, 50-60 mm of rain, and extreme rainfall rates of 30-50 mm in one hour. Such storms could lead to tree damage, power outages, property destruction, and hazardous driving conditions.
Residents are advised to seek shelter immediately if storms approach. Warm, moisture-rich air persists across southern Ontario, with a high of 27°C and a humidex of 35. This, combined with a low-pressure system from the U.S. Midwest, sets the stage for multiple rounds of severe thunderstorms. Conditions are expected to improve on Thursday with mostly cloudy skies and a chance of showers, followed by calmer weather Friday through Sunday as temperatures return to normal.
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