Stay alert for potential nighttime thunderstorms across Ontario

Friday's thunderstorm risk extends nearly 2,000 km from Texas to Ontario!

We’re on the lookout for the potential for overnight thunderstorms across portions of Ontario as a brief spell of summer-like warmth covers the region.

A centre of low pressure moving into the Great Lakes raised temperatures throughout the southern half of Ontario to end the week.

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This setup is similar to the one we saw earlier in April, which brought severe flooding to parts of Kentucky and Tennessee. In this case, however, the system's boundary will stall over the weekend from Ontario all the way to Texas--over 2,000 km! As a result, we're looking at a range of impacts across Ontario from this system.

Eastern Canada, US weekend forecast rainfall accumulation - April 18, 2025

After some rain earlier in the day, a cold front moving into southern Ontario will trigger additional rain and thunder arriving Friday afternoon and evening, lasting into the overnight hours. A widespread chance for rain and thunder will build across southern and eastern Ontario into early Saturday morning.

Ontario Friday night thunderstorm risk map - April 18, 2025

A few of the storms could approach severe limits with heavy rain, large hail, and strong wind gusts.

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The greatest chances of severe storms will exist through Grey-Bruce from the Huron shores east of Lake Simcoe. Monitor local weather alerts and stay aware of rapidly changing conditions in your area.

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Ontario Quebec Saturday thunderstorm risk map - April 18, 2025

The rainy conditions are expected to improve by Saturday afternoon, although stubbornly cloudy skies may continue to cast a layer of gloom over the rest of the day.

The sun could make a brief appearance on Sunday, but cooler temperatures, bitter winds, and possible scattered showers won't help improve the weekend's rainy theme.

Header image courtesy of Unsplash.

Stay with The Weather Network for more information and updates on your weather across Ontario.

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