01/03/2012 08:19 EST | Updated 03/04/2012 05:12 EST

Arctic Air Blast Chills Ontario, Quebec

CP File

A blast of Arctic air settled over Ontario and parts of Quebec on Tuesday, bringing double-digit sub-zero temperatures after a relatively mild December.

The City of Toronto issued a cold weather alert on Monday as temperatures dipped. The city issues a cold weather alert any time temperatures approach –15 C. The alert means extra shelter spaces are made available for the homeless.

The sudden freeze also extended into Ottawa and Montreal where temperatures fell to –18 C and –15 C respectively on Tuesday.

In Ottawa, the public health authority issued a frostbite warning as temperatures felt like –30 with the wind chill.

Snowfall of up to 50 centimetres is possible in areas around the southern end of Lake Huron and in and around London, Ont. The London airport has received a total of 41 centimetres of snow as of 9 a.m. Tuesday, Environment Canada said.

The cold air also formed snow squalls as it blew over the relatively warm waters of Lake Huron and Georgian Bay. Up to 25 centimetres of snow is possible in areas such as Collingwood, located on the shores of Georgian Bay, and Innisfil, just east of Barrie.

CBC meteorologist Nick Czernkovich said the freezing weather, while not unusual for January, is dangerous because it follows an unseasonably mild start to winter.

"We're not used to this," said Czernkovich. "People are going to go outside and they might be a little underdressed for it because we haven't seen these temperatures this year. Frostbite can set in in a matter of 10 or 20 minutes for exposed skin. It's not to say that you shouldn’t go outside, but dress appropriately."

But Kathryn Keeling said during the winter season, frosty temperatures should not come as a surprise.

"You know, you should expect it and dress for it," she told the CBC's Trevor Dunn on the streets of Toronto. "And if you don't, that's your problem."

Warmer temperatures in forecast

The good news is that the freeze is likely to depart as quickly as it arrived. Temperatures in the Greater Toronto Area are expected to rise by almost 15 degrees on Wednesday. The forecast is calling for temperatures of –1 C on Wednesday and 6 C on Friday.

Montreal and Ottawa will also see milder temperatures later in the week and into the weekend.

"The whole system is not lasting very long," said Czernkovich. "The Arctic air is going to pull out by the time we hit Wednesday, but it's sort of a one-off event that will give us this cold snap in the GTA."

Meanwhile, many people in the West were seeing warmer temperatures.

In Calgary, the temperature crept up to 7 C by early afternoon. In Edmonton, the temperature was hovering around 4 C.

In Vancouver, it was 8 C and there was a rainfall warning in effect, Environment Canada said.

Western provinces to see above seasonal conditions

CBC meteorologist Johanna Wagstaffe said that "most of the west" will remain above seasonal this week.

Wagstaffe said that Vancouver should also prepare for a Pacific system that will bring soaking rains and high avalanche risk for coastal mountains.

"Hardest hit will be the west coast of Vancouver Island where a total of 200 millimetres of rain is expected through Wednesday afternoon."

And on Prince Edward Island, some farmers were taking advantage of the unusually warm weather.

The mild winter gave Greg MacKenzie and his crew at MacKenzie Produce in Stratford a rare opportunity to harvest red cabbage. Usually, the farmers run out of time before the frosty temperatures arrive to bring all the produce inside.

But with almost no snow on the ground, they're getting another chance to salvage a crop that would otherwise have gone to waste.

"This is definitely a new thing for us," said MacKenzie, who has been farming for about 20 years. "The latest we've ever gone was Dec. 9. I guess and that was in 2004."