Severe thunderstorms and tornadoes
Get severe thunderstorm and tornado alerts
- use our Weather Information map to track storms near you
- download the WeatherCAN app and turn on alert notifications
- find the Thunderstorm Outlook for your area
About severe thunderstorms
Thunderstorms can create very strong winds, hail, heavy rain, and sometimes even tornadoes. Lightning is the most common danger associated with thunderstorms. As soon as you see lightning or hear thunder, you should find shelter inside a building or vehicle with the windows closed.
Protect yourself from severe thunderstorms:
- stay safe before, during, and after thunderstorms
- consult our Impact Guides to know what to expect when you receive severe thunderstorm or related-weather alerts
About tornadoes
Tornadoes can produce some of the highest wind speeds on the planet. Most Canadian tornadoes have maximum wind speeds under 180 km/h, but they can still cause serious damage.
When a tornado threatens, take shelter immediately, preferably in the lower level of a sturdy building.
All tornado events are rated using the Enhanced Fujita scale for wind damage.
Protect yourself from tornadoes:
- stay safe before, during, and after a tornado
- read about the potential impacts of a tornado
How we alert for severe thunderstorms and tornadoes
Our forecasters can now draw a shape around the area they predict will most likely be affected by a severe thunderstorm or tornado and target their warnings to only the people in that area. These targeted warning areas are also called “polygons”.
Our forecasters issue weather alerts on the WeatherCAN app and Canada.ca/weather, they are also shared with third-party weather providers like other mobile apps and the media. Certain severe thunderstorm and tornado warnings are also issued through the Alert Ready system directly to television, radio and cellular devices.
The change to targeted alerts means that when we issue a warning for a severe thunderstorm or tornado the warning area is much more precise. If you receive a warning notification on your phone, or elsewhere, you are much more likely to see dangerous weather.
When you receive a severe thunderstorm or tornado warning—act immediately!
Figure 1. Example of a targeted alert area where a yellow severe thunderstorm warning has been issued
Long description
Targeted yellow severe thunderstorm warning shown on the interactive Weather Information map on Canada.ca/weather. The warning area is roughly cone shaped, narrower on the left side, broadening towards the right, to show the direction of movement of the storm system it covers. The alert text is shown in a window to the left of the shape.
More flexible warnings
Thanks to the use of targeted alert areas, we can also issue multiple warnings for severe thunderstorms or tornadoes in the same alert zone at the same time. Polygons can also be split and merged, giving forecasters even more flexibility. This makes it possible to track different threats within the same storm system. You could see, for example, an orange severe thunderstorm warning and a red tornado warning at the same time, with safety information specific to each alert.
Figure 2. Example of two targeted warnings layered over each other
Long description
Targeted severe thunderstorm and tornado warnings over Moonbeam, Ontario, shown on the interactive Weather Information map on Canada.ca/weather. Both warning areas are roughly cone shaped, narrower on the left side, broadening towards the right, to show the direction of movement of the storm system they cover. The red tornado warning polygon falls within the orange severe thunderstorm warning polygon. The alert titles are shown in a window to the left of the shapes.
As a storm system moves, forecasters can update the targeted warning polygon, triggering alert notifications in new areas along its route. As with all other weather alerts, targeted warnings will trigger alert notifications from the WeatherCAN app (depending on your settings). Alert information is also always shared with third-party weather platforms and local media organizations.
All other weather alerts continue to be issued to traditional, pre-determined alert zones. We only use targeted alerts for severe thunderstorm and tornado warnings.
Missed or “near” alerts on the WeatherCAN app
Sometimes when using the WeatherCAN app you will receive an alert notification, but by the time you open the alert, the storm system has already moved out of your area. In these cases, you will see a message letting you know that the danger has passed.
Other times, you may see a notification for a severe thunderstorm or tornado warning “near” your location. In these cases, the content of the alert will explain that the warning affects a nearby area, and it is less likely that you will be directly at risk.
Severe thunderstorm and tornado warnings vs watches
Targeted alert areas will only be used for issuing severe thunderstorm or tornado warnings.
Severe thunderstorm and tornado watches will continue to use the existing pre-determined alert zones.
This means you will often continue to see both a severe thunderstorm or tornado watch and warning in the same area at the same time.
Learn more about the different types of weather alerts.
Alert Ready and targeted warnings
Alert Ready sends alerts directly to your phone, television, and radio. Environment and Climate Change Canada only issues specific weather-related Alert Ready alerts (for tornadoes and some severe thunderstorms).
The added precision of polygons will reduce the amount of Alert Ready alerts sent to mobile phones. However, Canadians will not see a noticeable change to the number of weather-related alerts that interrupt TV and radio programming .
Figure 3. Example of an Alert Ready message received on a mobile phone
Long description
An Alert Ready message received on a mobile phone. Text reads: “Emergency Alert / Alerte d’urgence. Environment Canada: TORNADO in this mobile coverage area. Take immediate cover in a basement or interior room if weather threat approaches. Shelter from flying debris if outside. Tornado warning, 8:56 p.m. EDT Tuesday 30 June /// [FRENCH] Environnement Canada : TORNADE dans votre zone actuelle de couverture cellulaire. Refugiez-vous sans tarder au sous-sol ou dans une pièce sans fenêtre en cas de temps menaçant. A l’extérieur, protégez-vous des débris projetés. Alerte de tornade, 20h56 HAE le mardi 30 juin.”
Thunderstorm Outlooks
Thunderstorm Outlooks give you an early heads-up when a thunderstorm is likely to develop—up to 36 hours in advance. We update Outlooks daily. Make sure to look for the time we issue the Outlook and the period it covers. The publication date and time show when we produced the map. All times on the map are local times.
A Thunderstorm Outlook is not an alert. It does not guarantee that a storm will develop, it only shows that the conditions are favourable. However, even if there is no Outlook for your area, it doesn’t guarantee no storms—thunderstorms can develop quickly!
Outlooks help you plan ahead, but no matter the forecast, always keep an eye (or ear) out for weather alerts!
Find the Thunderstorm Outlook for your area.
Related links
- Visit our Weather Information map for forecasts and alerts in Canada
- Learn how to use the Weather Information map
- Learn about Colour-coded weather alerts
- Discover our Weather Impact Guides
- See more about Lightning Safety
- Get Prepared for weather related hazard
- Read our Weather and meteorology glossary