TORONTO -- The national forecaster issued weather warnings for much of Ontario on Monday, citing extreme cold and heavy snow.
Environment Canada warned that parts of the province could see 20 centimetres of snow fall by Tuesday morning, with slightly more in the areas immediately surrounding the Great Lakes.
It says parts of northern Ontario can expect windchill values as low as -55.
The extreme weather prompted police to issue warnings about treacherous driving conditions, particularly during the Monday evening rush hour.
Provincial police Sgt. Kerry Schmidt says the highways in the Greater Toronto Area were crawling even before the start of rush hour.
He says that as of 3:30 p.m. police were investigating 20 crashes, including one that involved a transport truck.
"As it gets dark, it's going to be even more treacherous," he said. "So make sure you throw your headlights in the full on position."
He also encouraged people to stay at home if possible. Environment Canada predicted between 15 to 20 centimetres of snow for Toronto and Hamilton.
Toronto's Pearson International Airport tweeted that some airlines had cancelled or postponed flights due to the weather, and suggested travellers confirm their flight status before leaving the house.
The weather also led some places to close up shop earlier than usual. The University of Toronto and Ryerson University both cancelled evening classes on Monday.
