A snow squall warning is in effect for Southern Ontario, including Barrie, Collingwood, Orillia, Midland, Coldwater, Orr Lake, Lagoon City, Washago and Hillsdale.
Environment Canada says local snow squalls are expected Wednesday afternoon into Thursday morning.
Lake-effect snow, which could be heavy at times, is expected Wednesday afternoon, with local snowfall accumulations of 5 centimetres possible the evening.
As cold air moves over Georgian Bay late Wednesday afternoon or evening, more intense snow squalls will develop Wednesday night, Environment Canada says.
Snowfall accumulations of up to 15 centimetres are possible by Thursday morning in the heaviest areas, Environment Canada adds. Gusty northwest winds will also lead to local blowing snow with these snow squalls.
The snow squalls will begin to weaken Thursday morning, with additional accumulations of 5 centimetres possible by Thursday afternoon.
Environment Canada says snow squalls cause weather conditions to vary considerably – changes from clear skies to heavy snow within just a few kilometres are common.
Visibility will be suddenly reduced to near zero at times in heavy snow and blowing snow, the federal agency adds, and travel is expected to be hazardous due to reduced visibility.