Severe risk continues in Ontario, Quebec as storms hit muggy heat

A multi-day heat event continues in Ontario as the first week of July begins to wrap up. The high temperatures and humidity fuelled thunderstorms that prompted tornado warnings for regions of northern Ontario late Wednesday afternoon. As heat warnings remain in place for another day, so does the lingering risk for more thunderstorms on Thursday, with the potential for a swath of severe storms.

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THURSDAY

Areas: Northeastern, eastern, and southern Ontario; Quebec

Time: Afternoon and evening

Weather: The slow-moving cold front that prompted tornado warnings in northeastern Ontario late Wednesday afternoon continues to travel to southern Ontario and Quebec into Thursday, bringing with it a long awaited cooldown.

However, those looking for heat relief won’t get it until late Thursday. Expect widespread humidex into the high 30s in southern Ontario to persist throughout the day while the approaching cold front takes its time getting through southern Ontario. By Thursday afternoon it’ll be over the region, triggering another day of active weather.

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The highest risk for stronger, severe storms exists along the Lake Huron and Georgian Bay shores, through cottage country, and extending into the northern regions of the Greater Toronto Area (GTA), as well as southern regions of Quebec.

Another region of importance where we could see the potential for rotating storms that could produce tornadoes are parts of cottage country, North Bay, Mattawa, and southwestern Quebec. Due to the slow movement, some regions could pick up over 50 mm of rainfall in a few hours, raising concerns for localised flooding. Other hazards include nickel size hail, strong wind gusts upwards to 90 km/h, and the potential for one or two tornadoes.

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Temperature: Heat warnings continue to span southern Ontario and Quebec, where unseasonably warm temperatures kick off July. The uncomfortably muggy weather continues on Thursday, where humidex values of 40s are possible for Ottawa, Montreal, and much of southern Ontario, too.

Throughout the day today, as the cold front approaches, we will start to see temperatures cooling down for regions along the shores of Lake Huron and Georgian Bay, whereas cities along the 401 corridor, including the GTA and eastern Ontario, which are still locked in a hot, muggy, and, sticky airmass with humidex values into the low-mid 30s.

By Saturday, temperatures will still be hot, but the humidex will be lowered into the high 20s.

Below is a look at some of the impacts so far:

Brussels, Ontario. July 6, 2023 (Credit: Mark Robinson/The Weather Network)

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