The City of Toronto has issued an extreme cold weather alert in advance of a cold front that will bring bone-numbing wind chills, snow and the risk of a flash freeze on the roads.

Motorists are being urged to drive with caution because driving conditions in some parts of southern Ontario may take a turn for the worse later Friday as the wintry weather moves into the region.

Environment Canada said a flash freeze is possible because wet snow will freeze on untreated roads and fresh snow will fall as the temperature plummets.

The cold front will be ushered in with northerly winds and wet snow in the afternoon, followed by several hours of snow overnight. The system will hit the traditional snow belts in the afternoon and a line from Windsor through Toronto to Ottawa in the evening, Environment Canada said.

In a special weather statement, Environment Canada said the cold front is expected to hit the Greater Toronto Area in the mid-evening hours following the afternoon commute. About two to four centimetres of snow is expected to fall in the GTA in the evening, while as much as 10 cm is possible in southwestern Ontario.

Travel may remain hazardous for many regions after the cold front passes due to the risk of extreme cold, icy roads and blowing snow.

Temperatures hit 1 C in downtown Toronto Friday afternoon. They are expected to dropping to -10 C overnight with  the wind chill making it feel as cold as -25.

Shelter spaces added for homeless

Because of the frigid forecast, the city called an extreme cold weather alert to mobilize resources and add 172 shelter spaces for the city's homeless, so more have a safe and warm place to go.

During the alert, street outreach workers will try to convince homeless people to head indoors, and will offer free TTC tokens as a means of transportation to shelters.

People who see a vulnerable person who they think is in need of assistance are asked to call 311. People should call 911 for emergencies only.

The city is urging everyone to bundle up if they venture outdoors during the cold snap, and to limit their exposure to the cold.

As for the rest of the weekend, be prepared to bundle up.

Environment Canada said the snowfall will end Saturday morning before the temperature rises to a high of just -8 C. It will likely feel even colder because of strong wind gusts.

On Sunday, a mix of sun and cloud, high of -5 C and low of -11 C are expected.

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