Environment Canada said freezing rain is possible beginning in the morning or afternoon hours, before eventually switching over to rain.
“Areas near the shores of Lake Ontario are likely to remain above the freezing mark, and as a result should receive only rain,” the weather agency said.
Strong winds, along with localized flooding or ponding is also possible.
In places where there is ice accretion, some power outages could occur, the weather agency said.
Environment Canada said areas over the higher terrain of the Dundalk Highlands could see freezing rain persist into the late evening.
The temperature is then expected to shoot back up on Thursday, with a forecasted high of 14 C for Toronto.