Montreal's Pierre Elliott Trudeau International airport is reporting dozens of delayed and cancelled flights to Toronto, Quebec City and cities across the eastern U.S., as a major storm continues to wallop a large swath of Ontario, Quebec and the eastern seaboard.

Environment Canada is forecasting that this afternoon's heavy snowfall in the greater Montreal region will turn to snow mixed with ice pellets changing to freezing rain this evening before changing to rain overnight.

Warnings are also in effect for the Quebec City area, the Eastern Townships, Drummondville–Bois-Francs, Lanaudière, and the Laurentians area, among others.

8 hours of freezing rain?

David Phillips, a senior climatologist with Environment Canada, said the weather is part of what he described as the "possibly the strongest storm of the season" — one that will affect all of Eastern Canada.

"We could see about eight hours of freezing rain," Phillips said earlier Wednesday.

The combination of freezing rain and wind gusts will mean greater stress on branches and wires and increase the risk of power outages.

Hydro-Québec is braced for the worst. About 100,000 clients were without power by 10:30 p.m., including 78,000 in the greater Montreal area.

An estimated five millimetres of freezing rain are expected in most regions, though areas of the North Shore could see between 15 and 20 millimetres.

Difficult evening commute

upper lachine overpass flood

This underpass on Upper Lachine Road was flooded with slush an had to be closed . (Radio-Canada)

Drivers are urged to use caution on the roads and highways.

"On the island, roads are very slushy and icy," said CBC Montreal traffic reporter Lita Polson. "Off island, conditions are much worse – very icy. Just over the Île-aux-Tourtes [on Highway 40] and on the Laurentian Autoroute, there have been several major accidents."

Thursday morning could see heavy rain, with a high of around 5 C in the Montreal region.

Atlantic Canada will also experience nasty weather into tomorrow.

Travellers and those expecting people arriving at Montreal's Pierre-Elliott-Trudeau International Airport should consult the departures and arrivals pages for updates on the status of flights.