Environment Canada says a "significant" winter storm will drop varying amounts of snow across the province on Saturday, before turning to rain or freezing rain as temperatures increase later in the day and into Sunday.
The forecast is part of a wave of wintry weather expected to blast much of Canada this weekend.
Central and eastern Ontario will see the heaviest snowfall, at between 10 and 15 centimetres, while between two and five centimetres are expected to accumulate around and to the north of the Golden Horseshoe. Southwestern Ontario will see only trace amounts of snow, according to Environment Canada.
The freezing rain will be "brief" in most regions but could linger in communities including Barrie, Kitchener-Waterloo and Hamilton.
Special weather statements, but no warnings, are also in effect for Toronto, Peterborough and the Belleville area.
Temperatures will climb on Sunday, reaching the double digits in some areas, before a cold front is expected to arrive from the west, bringing strong winds and snow flurries.
Environment Canada warns that driving will be difficult throughout the weekend, considering the many changes in the weather.
The snow was falling by 1 p.m. in Toronto, leading to a wave of mostly minor traffic accidents around the city and outlying areas. Peel Regional Police were responding to at least 18 accidents by 2 p.m., while another eight were on the board at the Toronto Police Service.
Most of the accidents appear to be minor fender benders, officials said.