As Ontario welcomes summer with above-average temperatures, beachgoers are flocking to its lakes. But water quality can shift rapidly after heavy rain.
Rainfall drives bacteria levels-especially E. coli-through stormwater runoff and sewer strain. Toronto Public Health enforces a strict standard of 100 E. coli per 100 mL, one of the world's toughest. Swimmers should wait 24 to 48 hours after major storms.
Warming waters and increased precipitation also fuel harmful algal blooms, often appearing as bright green or “split pea soup.” The Ontario Spills Action Centre investigates reports and issues advisories.
Toronto Mayor Olivia Chow announced a 25% increase in lifeguard staffing this season. Experts recommend checking local advisories before heading to popular beaches like Woodbine, Cherry, Centre Island, and Sunnyside.
Public health warns that elevated bacteria can cause ear, eye, nose, throat, and skin infections, as well as stomach illness from swallowing contaminated water.