Blowing snow and ice pellets hit southern Ontario Sunday morning in what Environment Canada is calling a "crippling major winter storm."
Some say it may be the worst storm to hit the region in six decades.
Weather warnings have been issued for Ontario, southern Quebec and all of the Atlantic Provinces.
Road crews around the region are cleaning major highways in the Toronto area this morning ahead of the near record snowfall predicted by Environment Canada.
Airport officials said passengers throughout Central and Eastern Canada can expect delays and cancelled flights over the next two days. Air Canada said anyone who has a flight heading into or out of Toronto, Montreal, Quebec, Ottawa, or Halifax should check the status of flights before heading to the airport.
Toronto's Pearson International Airport cancelled more than 30 flights Saturday evening. Most of them were headed to U.S. cities already affected by winter storms.
Sunday's storm is expected to force delays and cancellations throughout the day.
"We're going to be looking at reduced operations due to snow clearing and de-icing,'' Toby Lennox of the Greater Toronto Airports Authority said Saturday.
"There will be delays, there will be cancellations.''
U.S. storm moves into Canada
The storm may dump as much as 40 centimetres of snow in some areas.
The major low pressure system barrelled toward Canada from Texas and moved into southwestern Ontario on Saturday. Along with snow it is expected to bring strong winds and freezing rain with it, Environment Canada's website reports.
"Significant blowing snow is expected to be a problem in all regions as strong northeast winds gusting to 70 or 80 km/h whip up the freshly fallen snow and cause whiteout conditions," it said.
Southwestern Ontario will experience the worst of the storm Sunday night as the system intensifies.
"The highest snowfall amounts may be around the west end of Lake Ontario into the Hamilton, Burlington and Niagara areas where very strong and cold northeasterly winds picking up extra moisture from Lake Ontario will help enhance snowfall amounts, with 30 to 40 cm quite possible by Sunday night," Environment Canada said.
The winter blast was expected to move toward southwestern Quebec and into the Gaspe region by Sunday, bringing between 15 to 30 centimetres of snow to the area.
The storm is expected to touch down in New Brunswick on Monday, with snow beginning ahead of the system on Sunday. Strong winds and blowing snow are expected for southern New Brunswick, which will receive 20 centimetres of snow and ice pellets near coastal regions.
Metro Halifax and the central mainland was expected to receive upwards of 15 centimetres of snow beginning Sunday afternoon that will change to ice pellets and rain by Sunday evening.
Environment Canada is warning motorists to use extreme caution and to only travel if necessary.