Severe Thunderstorm Watch in Ontario: Risk of Tornado, 110 km/h Winds, and Large Hail

Environment Canada has issued a severe thunderstorm watch for large parts of Ontario today, warning of dangerous weather conditions. Residents should prepare for winds up to 110 km/h, hail up to 4 cm, and the risk of a tornado. The alert covers areas from Chatham-Kent to Ottawa.

What Areas Are Under Watch?

The severe thunderstorm watch includes, but is not limited to:

• GTA & Surrounding Regions: Newmarket, Pickering, Oshawa, Barrie, Innisfil, Collingwood.
• Cottage Country: Muskoka, Haliburton, Kawartha Lakes.
• Eastern Ontario: Peterborough, Ottawa, Prescott-Russell.
• Southwest & Central Ontario: Owen Sound, Hanover, Shelburne, Dufferin County.

Environment Canada warns that damaging winds, large hail, and possible tornadoes could hit these areas this afternoon into the evening.

When to Expect the Worst

Forecasters expect the strongest storms between Tuesday afternoon and evening. A sharp cold front sweeping through Ontario will trigger severe thunderstorms.

Meteorologist Geoff Coulson noted that inland areas of the Great Lakes region face the highest risk. However, southern and eastern Ontario are also under threat as conditions evolve.

More Storms Through the Long Weekend

Unfortunately, this won’t be a one-day event. Back-to-back storm systems are set to affect Ontario through Saturday.

• Thursday Night: Storms from the U.S. Midwest move into southwestern Ontario.
• Friday: Another round of storms, with severe risks in eastern Ontario and into Quebec.
• Saturday: Scattered showers and possible pop-up storms persist.
  

Despite these forecasts, experts say the Victoria Day weekend won’t be a total washout.

Staying Safe: Tornado & Thunderstorm Tips

Environment Canada urges Ontarians to stay alert and follow these safety tips:

• Monitor weather alerts from official sources.
• Take shelter immediately if a tornado threatens—preferably in a basement or interior room.
• Stay away from windows, outside walls, and doors.
• Secure outdoor objects that could become dangerous in high winds.
• If driving, seek sturdy shelter or find low ground like a ditch if a tornado approaches.
• Never underestimate lightning—when thunder roars, go indoors.
  

The Weather Shift After the Storms

Tuesday could be one of the warmest and most humid days of spring, especially in Ottawa, with highs reaching 23°C.

However, temperatures will drop sharply by Wednesday, with Toronto expecting a daytime high of just 13°C. Cooler, more seasonal weather will continue into the weekend.

Stay updated with the latest alerts from Environment Canada and local emergency services. Conditions can change rapidly during severe thunderstorms.

Have you ever experienced a severe thunderstorm or tornado in Ontario? How did you prepare? Share your stories below.

More…

• https://www.insidehalton.com/news/tornado-tuesday-ontario-warning/article_4f945bfa-5f4c-5ec9-b0f6-4fedf9879a17.html
• https://www.theweathernetwork.com/en/news/weather/forecasts/severe-storms-may-interrupt-long-weekend-plans-in-southern-ontario-victoria-day
• https://sydenhamcurrent.ca/2025/05/15/risk-of-a-tornado-as-a-severe-thunderstorm-watch-is-issued-in-chatham-kent