People in southern Ontario were being hit with a blast of snow Saturday, a system which is expected to arrive in Quebec in the evening and Eastern Canada on Sunday — while people in Western Canada were bracing for extreme cold or heavy rain, with freezing rain expected in some areas.

Driving conditions in communities in the Niagara Region and eastward to Toronto were already becoming treacherous before noon.

A multi-vehicle crash in Mississauga involving as many as 20 vehicles closed all westbound lanes of the Queen Elizabeth Expressway between Erin Mills Parkway and Winston Churchill Boulevard around 11 a.m. ET. The highway was closed for about two hours and has since been reopened.

qew-crash

One of about a dozen mangled cars await processing after a 20-vehicle pileup on the Queen Elizabeth Expressway on Saturday. (Charlsie Agro/CBC)

According to CBC's Charlsie Agro, a city bus parked at a parking lot near the highway was turned into a makeshift reporting centre. A dozen drivers and passengers were inside filling out police and collision reports. Paramedics were checking out the passengers, some of whom complained about back and neck injuries, but no major injuries were reported.

GO Transit has suspended all bus service to and from Union Bus Terminal due to poor weather conditions. Some train trips are also cancelled as a result.

A winter storm warning has been issued for southern Ontario, including Toronto.

The city could get hit with up to 15 centimetres of snow, Environment Canada said. Meanwhile 25 centimetres of snow was forecast to fall west of Toronto in Hamilton, Ont., and the Niagara Region by Saturday night.

The fast-moving storm will head into the Maritimes on Sunday and could dump 20 to 30 centimetres of snow in some areas.

Travel advisories issued

A winter storm warning has also been issued for the Montreal area. Environment Canada said people in the region can expect 15 to 30 centimetres of snow, beginning Saturday evening.

The storm will also bring blowing snow to the region. The wind will make it feel as cold as –28 C Saturday night, with temperature rising to –12 C by Sunday morning.

Both Air Canada and WestJet have issued travel advisories for major airports from Toronto to St. John's. Travellers are advised to check the status of their flights before heading to the airport. The two airlines are also offering travellers the chance to reschedule their flights ahead of the storm without penalty.

The storm has already caused U.S. airlines to cancel about 1200 flights as of Saturday night, mostly in the Midwest and Northeast, according to The Associated Press.

To the west, freezing rain warnings are in effect in and around Edmonton. A mix of rain and about five centimetres of snow is expected to create potentially dangerous driving conditions.

Wind chill warnings are in effect for the northern portions of Saskatchewan and Alberta. Temperatures throughout the day could feel like –40 C with the wind chill in those regions. Early Saturday, the wind chill made it feel closer to –50 C.

Heading south to areas including Pincher Creek, Alta., the forecast calls for strong winds gusting to about 100 km/h.

In B.C., a strong Pacific frontal system will continue to produce heavy rainfall over the inland sections of the North Coast. As of 3 p.m. local time, 50 millimetres of rainfall has been reported since Friday night. Additional amounts of 20 to 30 millimetres are forecast Saturday night before the rain tapers off to a few showers overnight.

With files from Associated Press