Home › Weather › Severe Weather Storm
Live forecasts update automatically; written guidance last reviewed 16 June 2026 by the True North Brief Weather Desk. Data from Environment and Climate Change Canada and other national met services via Open-Meteo.
A severe weather storm in Canada is defined by Environment and Climate Change Canada as a storm producing winds of 90 km/h or higher, hail at least 2 cm in diameter, heavy rain, or a tornado. These storms threaten life, property and infrastructure each year, especially from late spring through early autumn.
What qualifies as a severe weather storm in Canada?
Environment Canada issues severe thunderstorm warnings when radar or reports indicate any of these criteria are imminent or occurring: wind gusts ≥90 km/h, hail ≥2 cm, heavy rainfall capable of flash flooding, or a confirmed tornado. A severe storm may also include widespread damaging straight-line winds, known as a derecho, or a prolonged period of freezing rain that accumulates to hazardous levels. The agency uses a colour-coded alert system—Advisory, Watch, Warning—to communicate increasing threat levels.
How should Canadians prepare ahead of severe storms?
Preparation begins with checking the current weather warning for your region and knowing the difference between a Watch (conditions possible) and a Warning (conditions imminent). Have a 72-hour emergency kit with water, food, flashlights, and a battery-powered radio. Secure outdoor furniture and vehicles, and identify the safest room in your home—basement or interior room without windows. For real-time updates, refer to Canada’s weather hub or local forecasts.
What is the difference between a severe thunderstorm watch and a warning?
A watch means conditions are favourable for severe storms in your area—stay alert. A warning means severe weather is occurring or imminent—take immediate shelter. Warnings are issued for specific, short-duration threats.
When does severe storm season begin in Canada?
Severe storm season typically runs from late May through September, with the highest frequency in June and July. However, severe storms can occur as early as March in southern Ontario and as late as October in the interior.
What should I do if a tornado warning is issued?
Take cover immediately in a basement or small interior room on the lowest floor, away from windows. Do not seek shelter under an overpass. If in a vehicle, abandon it and lie flat in a low-lying area. Stay there until the warning ends.