Toronto is under a winter weather travel advisory with five to 10 centimetres of snow expected to fall by Saturday evening.
Environment Canada says accumulating snow on untreated roadways could create "hazardous" conditions.
Snow will begin falling over southwestern Ontario Saturday morning and is expected to spread eastward through the day.
"Motorists should expect hazardous winter driving conditions and adjust travel plans accordingly," the weather agency said.
"Be prepared to adjust your driving with changing road conditions. Take extra care when walking or driving in affected areas."