Seasonal Flood Safety Message: Be aware of flooding risk due to thunderstorms

The summer weather has finally arrived! The warm season brings longer days and more fun outdoors. However, it also comes with severe weather hazards such as thunderstorms and flooding. 

Thunderstorms can suddenly develop during the warmer months and are often accompanied by strong winds, hail, lightning, and heavy rain. In some areas, especially urbanized locations, thunderstorms can cause flash flooding when large amounts of heavy rain occur in a short period of time. 

Forecasting and flood messaging for thunderstorms

It can be challenging for weather forecasts to accurately predict where and when thunderstorms will form. We rely on the weather forecasts and alerts from partner agencies such as Environment Canada, to assess the risk and severity of flooding resulting from sudden thunderstorms. If the forecast indicates that flooding is possible or about to occur, we issue flood messages to designated individuals within municipalities, partner agencies, and the media. Members of the public who self-subscribe to receive updates on the flood situation receive a notice of flooding risk in their email. Learn more about flood messages and how to self-subscribe.

Thunderstorm forecasts provided by other agencies often have very low confidence in exactly where, when, and how much rain will fall. As a result, it is very challenging to issue an accurate flood message for every forecasted (and sometimes un-forecasted) thunderstorm due to the high uncertainty. During severe rain events, we monitor the real-time weather and watershed conditions within the watershed jurisdiction, using tools such as radar and water level and precipitation monitoring gauges. 

Summer Flooding Safety Preparedness Tips

Flooding occurs when rivers and streams rise over their banks and spill into the surrounding land. Smaller streams and streams that flow through the urbanized areas can be considered ‘flashy’, which means that large amounts of precipitation over a short period of time can cause water levels in river systems to rise very quickly with little warning, sometimes in a few hours. 

As a reminder: 

• Stay away from riverbanks and avoid recreational activities in watercourses during storm events, especially during thunderstorms.
• Never drive through, walk in, or stand in any moving water. 
• Avoid low-lying areas such as road underpasses and walkways.
• Stay informed on thunderstorm warnings through local media outlets. Keep a battery-powered or wind-up radio in your home to stay up-to-date during power outages.
• Download the WeatherCAN app from Environment Canada WeatherCAN - Canada.ca. The app provides weather information and alerts for your current and saved locations.
• If you are instructed by emergency officials to evacuate, do so immediately.
• If you or others are in danger, call 911 immediately. 

Learn more about summer weather hazards and safety tips at www.canada.ca.

For more information about regional water levels and seasonal changes, contact your local Conservation Authority.