Another big blast of winter caused commuter chaos on Wednesday as heavy snow blanketed the GTA.

A snowfall warning was in effect for Toronto and the GTA for most of the day and triggered many delays and cancellations.

Environment Canada issued the warning in the morning for Toronto, Halton Hills, Milton, Mississauga, Brampton, Caledon, Vaughan, Richmond Hill, Markham, Pickering, Oshawa and southern Durham Region.Those warnings have since ended. Total snow amounts spanned from 14 to 28 centimetres by the evening.

On Wednesday, the City of Toronto issued an extreme cold weather alert, which will be in effect until further notice.

Such an alert is issued in the morning when Environment Canada predicts extreme weather conditions such as a blizzard, ice storm or a sudden drop in temperature. It also allows the city to open up more shelters for the homeless.

This is the fifth alert the city has issued this winter, officially covering 19 days. In 2008-2009, the season with most extreme cold alerts, the city was under an alert for 27 days.

A snowfall warning was already issued Tuesday for Burlington, Oakville, Niagara and Hamilton, with up to 20 centimetres possible in the Hamilton and Niagara regions.

The TTC temporarily shut down the Scarborough RT at 12:30 p.m. to allow its work crews to clear ice and snow from the system. By the evening TTC spokesperson Brad Ross said the SRT would not resume service on Wednesday but service would be back up and running by Thursday morning. Shuttle buses are running between Kennedy and McCowan stations.

Drivers in the GTA encountered a slow and messy morning commute on Wednesday due to the accumulating snowfall.

680News airborne traffic reporter Darryl Dahmer said at one point, there was a 55-kilometre backup on the westbound Highway 401 heading out of Oshawa. Although the backups are not as extensive as that one, they are still problematic.

Environment Canada had warned the heaviest snowfall was expected on Wednesday morning and the city said that would be an issue.

“[The snow] is unfortunately going to cause some problems not only for commuters, but also for ourselves in trying to plow the snow on the main roads,” Peter Noehammer with Toronto Transportation Services said.

Plowing operations are already underway on the city’s expressways. The city has 200 salt trucks, 600 road plows and 300 sidewalk plows in its snow-clearing arsenal.

Beck Taxi said it expects to receive around 2,000 calls an hour for a taxi and that wait times for some areas are up to 70 minutes. Meanwhile, the Canadian Automobile Association (CAA) has received over 1,400 calls for service in south central Ontario (including Toronto), but warns that callers can expect delays due to the road conditions. The wait for a tow truck in the GTA is over 90 minutes.

The snow over the region is due to a low pressure system that tracked from the United States. The weather agency said several centimetres of snow fell overnight from Sarnia to the GTA and east to Kingston.

The forecast calls for gusty northeast winds to develop and could lead to blowing snow.

Drivers were advised to allow for extra time due to continuing snowfall and reduced visibility due to blowing snow.

Despite the tapering off of snow, Environment Canada has issued a special weather statement for local blowing snow which may persist through mid evening.

School buses were cancelled in Halton, Peel, York and Dufferin-Peel and evening classes were cancelled at many schools across the GTA. Click here to see our full list of school bus cancellations and school closures.

GO Transit warns it expects possible service delays due to overnight snowfall. Click here for service updates.

Air Canada, WestJet and Porter Airlines have all issued travel alerts warning of delays and cancellations, due to the weather in the GTA and also in the U.S. Northeast.

More than 190 flights have been cancelled at Pearson International Airport due to the storm in the U.S., affecting Chicago, New York and Boston. Click here to check your flight status.

There are a handful of cancellations at Billy Bishop Toronto City Airport but only affecting Air Canada flights. Click here to check your flight status.

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Snow plow operators on Trafalgar Road in Oakville prepare for a busy day on Feb. 5, 2014. CITYNEWS.