Parts of southern Ontario could get 20 to 40 centimeters or more of snow by Sunday, Environment Canada warned.
Lake effect snow is expected to be heavy from Lake Huron and Georgian Bay throughout Saturday, the weather agency said in a warning early Saturday.
The following areas are under blizzard warnings: Newmarket, Georgina, North York Region, Barrie, Collingwood, Hillsdale, Uxbridge, Beaverton, North Durham Region and Orillia.
If it snows in one area, more than 40 centimeters of snow can fall, says Environment Canada.
Heavy and blown snow can suddenly reduce visibility to near zero. People are advised to postpone non-essential travel until the weather improves.
Snowfall should be less intense on Sunday, Environment Canada said.
To the north, Bracebridge and Gravenhurst are also under snow squall warnings, with 15 to 25 centimeters or more of snow expected to fall on Saturday afternoon.
While Toronto is not under a weather warning, the city opened its warming centers on Friday as temperatures were expected to drop below -5 degrees Celsius.
Temperatures dropped to -4 degrees Celsius overnight, according to data recorded at Toronto Pearson International Airport.
The city is forecast to see a high of -2 degrees Celsius on Saturday, with temperatures expected to feel like -13 degrees Celsius due to wind.
Earlier this week, Environment Canada warned that some areas north of the GTA could receive up to 60 centimeters of snow.
