Severe Thunderstorms and Summer-Like Heat in Southern Ontario This Week

Southern Ontario will experience a taste of summer-like temperatures early this week, but it will come with a chance of severe thunderstorms, especially on Tuesday, April 29. A Colorado low will make its way across the Great Lakes, ushering in warm, humid air and an elevated risk of severe weather.

The storm system will bring temperatures in the mid- to high 20s, and some regions in southwestern Ontario may hit the 30°C mark, making it the first 30-degree day of the year in Canada.

Severe Thunderstorm Risk on Tuesday

While the warmth will feel like summer, it may trigger thunderstorms later in the day, with a 60% chance of rain across southern Ontario. The main hazards associated with these storms include large hail, strong winds, and heavy downpours. 

There is a low, but non-zero risk of isolated tornadoes, especially if the storms remain isolated. Conditions are favorable for strong updrafts that could lead to severe weather, and the greatest storm risk appears to be between 2 p.m. and 7 p.m. on Tuesday.

Weather Timeline and Details

• Monday: Sunny with mild temperatures around 16°C, and winds picking up to 20 km/h in the afternoon.
  
• Tuesday: Expect mostly cloudy skies, a 60% chance of rain, and the warmest day of the week with temperatures reaching 25°C. The risk of thunderstorms increases as the day progresses.
  
• Wednesday: Expect cooler temperatures around 16°C with sunny skies and light winds.
  
• Thursday: Cloudy conditions will return with a 60% chance of rain. Temperatures will drop to around 10°C, and rain will continue into the night.
  
• Friday and Saturday: Partly cloudy with a 30% chance of showers and temperatures hovering around 14°C on Friday, and 10°C on Saturday.

What to Expect

• Heat and humidity will push dew points near 20°C on Tuesday, a highly anomalous reading for late April.
  
• While there’s a strong chance of localized downpours, these storms are expected to move quickly, reducing the risk of flooding.
  
• Wednesday will provide a brief cool-down, but the warmer pattern will return towards the weekend.
  

Preparing for the Storms

Stay tuned to the weather updates and monitor any storm watches and warnings as they are issued by authorities. Thunderstorm season is ramping up, and it’s essential to stay informed about the rapidly changing conditions.

Have you experienced severe weather in southern Ontario recently? What preparations do you take during thunderstorms? Let us know in the comments.

More…

• https://www.theweathernetwork.com/en/news/weather/forecasts/southern-ontario-to-be-teased-by-summer-like-warmth-with-severe-storm-risk
• https://www.insauga.com/25-c-temperatures-and-thunderstorms-to-hit-southern-ontario-this-week
• https://instantweatherinc.com/article/ontario/2025/4/25/tornado-tuesday-confidence-continues-to-build-for-ontario