Southern Quebec was walloped with its first major storm of the season, with hazardous conditions, numerous accidents reported and flight delays.
Up to 40 centimetres of snow are expected by this evening.
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Many flights in and out of Montreal's Pierre Elliott Trudeau International Airport are delayed or cancelled.
The airport recommends checking the status of your flight before going to the airport.
The backlog in Montreal, Toronto and Ottawa is also causing problems in other provinces.
Roads and sidewalks are treacherous and snow is expected to accumulate throughout the day.
Dozens of cars go off road
Transports Québec is urging drivers to stay off the roads if possible.
"The roads are covered in snow with reduced visibility so you have to be extremely careful today," spokesperson Sarah Bensadoun said.
Sûreté du Québec spokesperson Mélanie Dumaresq says several dozen cars went off the road this morning in the Montreal area.
However, no major accidents have been reported so far.
Earlier this morning, over 2,000 Hydro-Québec customers in Montreal were without electricity.
The affected areas included downtown Montreal, Outremont and LaSalle.
Power was restored by mid-morning.
Snow to halt this evening
Southern parts of the province are the most affected by the storm, including the Montreal area, the Laurentians and the Eastern Townships, and the Ottawa Valley, where 30 to 40 centimetres are expected.
About 15 centimetres are expected in the Quebec City region.
Winds of 30 to 60 kilometres an hour are also expected, particularly over the St. Lawrence Valley.
Snow is expected to quickly taper off this evening.
Montreal's winter storm hasn't stopped cyclists apparently. pic.twitter.com/nZNY98AKVk— @KayLaframboise
Environment Canada also issued freezing rain warnings for portions of southern Ontario, including the Bruce Peninsula and areas around Lake Simcoe.
The storm hitting Ontario and Quebec is part of a system that producing tornadoes and flooding in the U.S. Midwest and Southwest.
More than 40 people were killed in the United States during the Christmas holidays, including 11 in the Dallas area when twisters hit.