Freezing rain has caused hundreds of road accidents in southern Ontario, one involving a truck loaded with hazardous liquid oxygen. The same weather system is also moving east, dumping snow on much of Quebec and the Maritimes.

The truck turned over on its side Monday afternoon on a busy Toronto highway. No injuries were reported, but a hazardous materials team evacuated the surrounding area.

With temperatures falling, the ice pellets are expected to turn to snow later in the day -- as much as 10 centimetres in some areas.

The icy conditions slowed morning rush-hour traffic to a crawl in many parts of the Toronto area, with even slow-moving cars sliding out of control on smaller highways.

School bus service has been cancelled in most districts east of Toronto, in the London area, and across eastern Ontario.

At Pearson International Airport in Toronto, workers are frantically trying to de-ice aircraft, but not fast enough to avoid a backlog of flights. More that 50 flights have been cancelled, mostly to Canadian and U.S. destinations, while plenty of others have been delayed.

As usual during storms, travellers are advised to call ahead to check their flight status before heading to the airport.

Police have been called to more than 100 accidents on provincial highways, most of them single-vehicle collisions. No serious injuries have been reported.

The storm is moving east, so winter storm watches and snowfall warnings are being issued for southern Quebec and most of the Maritimes.

People living east of Montreal face up to 25 centimetres of snow tonight, and icy conditions have caused several car crashes.

Eight students were injured when their bus tipped over on a highway near Drummondville. The vehicle had Virginia licence plates, and reports said the students -- all in their 20s -- were on a ski trip.

The forecast also calls for about 15 centimetres of snow between this afternoon and Tuesday morning in most of Nova Scotia, with possibly greater amounts in northwestern areas. Environment Canada says the snow could be mixed with ice pellets and freezing rain in coastal areas.

A heavy snowfall warning is in place for Prince Edward Island and southeastern New Brunswick, with more than 15 centimetres expected.

"Later this week, we're going to see clearly some cold air arrive to eastern Canada," Environment Canada senior climatologist David Phillips told Canada AM Monday morning.

"It's beginning to look like winter and it's going to feel like winter over the next couple of days."

Phillips says the storm finally brings the long-anticipated end to the warm temperatures most of eastern Canada has been enjoying.

"This is typically, across Canada, the halfway point when probably we can say there's more winter behind us than ahead of us. But for some of us in the East, it's just arrived -- much later than normal."

West Coasters, who have experienced more than a dozen rain or snowstorms since November, are not being spared today either.

A snowfall warning has been issued for Greater Victoria, Greater Vancouver and the Fraser Valley. There's also a wind warning for northern Vancouver Island, the central and north coast, and the Queen Charlottes.