Prepare for Summer Storms: Seasonal Safety Tips and Reminders

As summer arrives, it’s important to stay alert for thunderstorms. These storms can develop quickly and bring heavy rain, strong winds, lightning, and sometimes hail. Toronto and Region Conservation Authority (TRCA) advises everyone to be aware of the flooding risks associated with these storms.

raindrops splash to the ground during a summer storm

Rivers within TRCA’s jurisdiction are “flashy,” meaning that intense rainfall over a short period of time can cause water levels to rise quickly, often within minutes.

Urban areas are more prone to flooding during thunderstorms because surfaces such as roads, sidewalks, and parking lots do not absorb water, leading rainwater to flow quickly into drainage systems and rivers.

flood event in City of Vaughan
A flooded park trail and pedestrian bridge in City of Vaughan.

Floods can develop quickly during thunderstorms, so it is important to remain cautious and stay safe.

Summer Flood Safety Tips

  • Avoid recreational activities such as walking on trails, hiking, and cycling, and in-water activities, such as canoeing, kayaking, fishing, and swimming near rivers and other water bodies during and immediately after thunderstorms.
  • Do not drive through flooded roads or fast-moving water and avoid low-lying areas like underpasses.
  • Stay updated on weather alerts via local radio, television, mobile apps, or other alert systems.
  • If emergency officials order an evacuation, follow the instructions provided by the first responders.
  • If you are in immediate danger, call 911.

Claireville Dam
Claireville Dam, July 2018. TRCA owns and operates 12 dams, six dikes, and nine flood control channels within its jurisdiction.

How TRCA Keeps You Safe During Severe Weather

  • TRCA’s Flood Forecasting and Warning Program monitors weather and watershed conditions to warn about potential flooding.
  • When significant rainfall is forecasted, an on-call Flood Duty Officer (FDO) assesses flood risk.
  • TRCA issues flood messages to stakeholders and subscribers when heavy rainfall is expected to cause river flooding. Sign up to receive flood messages.
  • During severe weather, TRCA staff use radar, weather forecast models, and TRCA’s Flood Monitoring Gauging Network to track real-time weather and watershed conditions. Visit to view real-time water levels and rainfall amounts.

In the Greater Toronto Area (GTA), severe summer storms can occur due to various weather systems and atmospheric conditions. These include:

  • Severe Thunderstorms: Thunderstorms can develop quickly during the warmer months, bringing strong winds, hail, lightning, heavy rain, and sometimes even tornadoes. Forecasting the exact location and amount of rainfall from these storms is challenging.
  • Tropical Storms and Hurricanes: Occasionally, Ontario can be impacted by remnants of Atlantic hurricanes, which bring heavy rain and strong winds, and can cause flooding. The Atlantic hurricane season runs from June 1 to November 30 each year.

The GTA Has Experienced Significant Rainfall from Hurricane Systems in the Past!

Hurricane Hazel was Ontario’s worst storm on record.

On October 15-16, 1954, Hurricane Hazel brought unprecedented rainfall and devastating floods to Toronto, resulting in 81 deaths and leaving thousands homeless. This event reshaped flood management policies in Ontario. Learn more at

black and white archival photograph shows the flooding that resulted from Hurricane Hazel in October 1954
Curiosity seekers on the Etobicoke side of the Lawrence Avenue bridge look over into Weston. October 16, 1954.

As we commemorate the 70th anniversary of Hurricane Hazel this year, the flooding and devastation that resulted serves as a reminder of the importance of flood preparedness.

Learn more about summer safety and sign up to receive TRCA flood messages.