Generally, the water surrounding the Toronto Islands is safe for swimming, but it is subject to daily monitoring by Toronto Public Health. The islands are home to several "Blue Flag" certified beaches, such as Ward’s Island, Centre Island, and Hanlan’s Point, which meet high international standards for water quality. However, safety can change rapidly based on the weather. After a heavy rainfall, bacterial levels (specifically E. coli) often spike due to urban runoff, and the city will post "Red Flags" or advisory signs warning people not to enter the water for 24 to 48 hours. In 2026, the city uses an updated real-time monitoring system that you can check on the "Swim Guide" app or the City of Toronto website. It is also wise to watch out for "Blue-Green Algae" blooms in late summer, which can be harmful if swallowed. As long as the "Blue Flag" is flying and there hasn't been a recent storm, the water is a refreshing and safe escape from the city heat.