Severe thunderstorms are thunderstorms with one or more of the following conditions:
Wind gusts of 90 km/h or greater
Hail of 2 centimetres or larger in diameter
Heavy rainfall when 50 mm or more is expected within one hour over the Prairies, or 25 mm or more in one hour over the
The threat level on the Thunderstorm Outlook is determined using a combination of hazard thresholds, likelihood of occurrence and impacts
based on known vulnerabilities and exposure. In each province and territory, the highest threat level is indicated on the associated risk
matrix. If there are two polygons of equal threat level within one province or territory, the polygon that encompasses the highest impact
will be the one indicated on the risk matrix.
The forecaster’s confidence in the individual hazards reaching the indicated value, as well as their confidence in the location of the
thunderstorms and the overall development of the thunderstorms within the highest threat level polygon are also indicated in the Confidence
The thunderstorm outlook regular issue has ended for the season. Please go to the ECCC Weather Office page for pertinent weather information.