Severe storm, flood threat shifts into eastern Ontario, Montreal Tuesday

Ontario's storm risk shifts east into the Ottawa-Kingston region in Ontario on Tuesday, as well as the Montreal region in Quebec.

Parts of southern Ontario had a loud night as thunderstorms and heavy rains continued through the overnight on Monday and pre-dawn Tuesday. Now, as the region attempts to dry off, the storm risk will shift into eastern Ontario on Tuesday.

A stalled upper-level trough will bring a potential for severe, flooding storms to the Ottawa-Kingston region on Tuesday, as well as to Montreal. Some locales could see 50-80+ mm of rainfall from the slow-moving storms.

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The most serious danger will be if storms frequently pass over the same locations, causing rainfall totals to rapidly rise. Localized flooding, low visibility and dangerous driving conditions are all conceivable.

Ontario and Quebec Tuesday severe storm risk - July 28, 2026

Flooding risk elevated with more thunderstorms on Tuesday

Showers begin Tuesday morning, with the severe thunderstorm potential increasing through the day as temperatures increase.

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Ontario and Quebec Tuesday afternoon forecast storms - July 28, 2026

The severe risk will remain east of the low as it moves northward, putting the Laurentians and Ottawa Valley at the greatest risk of localized flooding as that is where we will likely see training thunderstorms drop the most rain.

Showers and heavy downpours may continue overnight Tuesday into Wednesday, but the bulk of the storms will stay in Quebec.

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Stay with The Weather Network for the latest updates for Ontario.