Environment Canada has issued a rainfall warning for Toronto, saying the city is expected to receive significant amounts of rain through to Thursday morning.
The rain began falling on Tuesday night.
Amounts of 50 mm to 60 mm are expected by early Thursday and a few local areas could receive up to 75 mm of rain, according to the federal weather agency.
“Rain, at times heavy, is expected,” it said in the warning.
The forecast calls for showers and isolated thunderstorms to continue through to at least Wednesday night.
A cold front and a low pressure system laden with moisture from the American midwest is bringing the “widespread rainfall event” to Toronto, the agency said.
Residents are reminded that heavy rain can cause flash floods and water to pool on roads.
If visibility drops while driving, motorists are urged to turn on their lights and keep a safe following distance from other vehicles. Flooding in low-lying areas is possible.
Environment Canada says it issues rainfall warnings when “significant” rainfall is expected.