Bundle up, Toronto — the city has issued its first extreme cold weather alert of the season.

Toronto Public Health says the alert comes in consideration of the sudden temperature change and a projected wind chill of -18 overnight. It activates local services that focus on getting vulnerable residents inside, including additional shelter beds and overnight street outreach.

The city is also advising Torontonians to wear layers, stay dry, and seek shelter if you normally spend long periods of time outdoors.

Based on information from Environment Canada, <a href="https://twitter.com/TOPublicHealth?ref_src=twsrc%5Etfw">@TOPublicHealth</a> has issued an Extreme Cold Weather Alert today for Toronto that will be in effect until further notice. More info in this news release <a href="https://t.co/kbmBV4lQlJ">https://t.co/kbmBV4lQlJ</a> <a href="https://twitter.com/hashtag/TOnews?src=hash&ref_src=twsrc%5Etfw">#TOnews</a> <a href="https://t.co/wEFFuwpJjO">pic.twitter.com/wEFFuwpJjO</a> —@TorontoComms

The Greater Toronto Area and most of southern Ontario are also under a winter weather travel advisory. Toronto police are warning commuters, particularly motorists, to adapt to difficult driving conditions.

A cold front is coming in from northern Manitoba and the Arctic that will cause temperatures to drop Thursday afternoon, according to Peter Kimbell, warning preparedness meteorologist with Environment Canada.

The federal agency's advisory warns that snow and "rapidly falling temperatures" could make road conditions treacherous this afternoon and evening.

"As this front passes, temperatures will drop below the freezing mark and scattered rain showers will change to flurries," the federal agency said in its advisory.

"As a result, untreated surfaces could become icy and slippery."

Police are reminding motorists to 'drive according to conditions' as wintry weather sets in. (ICI Radio-Canada)

In anticipation of the first taste of winter weather, the Toronto Police Service issued a reminder Thursday morning that motorists should "drive according to conditions."

That includes reducing speeds on elevated parts of the road, such as bridges, overpasses and expressways.

Police are using the acronym WINTER to list their tips for getting around safely.

W: Windshield washer fluid is full.

I: Information on current road and weather conditions.

N: Need to clear snow off your car.

T: Tire tread checked and tires changed as necessary.

E: Expect the unexpected.

R: Reduce your speed.

Motorists need to plan ahead when it comes to how they are going to drive in poor weather, Const. Clint Stibbe of the Toronto police Traffic Services division, told CBC Toronto.

"You need to be driving 10, 20, 30 seconds ahead of where you actually are," Stibbe said. "And unfortunately we don't tend to do that."

According to Stibbe, speed is a driver's "biggest enemy. The faster you go, the harder you're going to find it to stop."

Even on dry pavement, every time a driver doubles his or her speed, stopping distance quadruples, he said. Once water or ice is added to the equation, "you're looking at stopping distances 10 or even 15 times what they would normally be."

And for anyone who got their snow tires on early and thinks they are invincible, think again, Stibbe said.

"I don't want anybody to think for a minute that that is going to save them no matter what they do. A lot of people get a false sense of security thinking that by putting those tires on they can do anything they want," Stibbe said.

"That is not the case. Physics still apply. And when you exceed the capability of those tires and the roadway, you're in trouble."

'It will be unseasonably cold and it will be a shock to everybody,' Kimbell said. (Andrew Lupton/CBC)

'It will be a shock'

While the forecast high for the city on Thursday is 9 C, rain is expected to move in this afternoon with winds gusting to between 30 and 50 km/h.

The temperature will drop in the afternoon to 2 C, and it's sometime after 8 p.m. that conditions will be at their worst, Kimbell told CBC Toronto early Thursday morning.

"It will be unseasonably cold and it will be a shock to everybody," Kimbell said.

That shock will come in the form of near record low temperatures overnight Thursday and into Friday, when the temperature will dip to -10 C. With that cold front, the rain will turn to flurries, with local snowfall amounts of about 2 cm possible.

Flurries could continue into Friday morning, when the temperature will remain low at -1 C.

Meanwhile, other parts of southern Ontario, mainly to the north of Toronto, are also under a snow squall watch which says heavy blowing snow could "significantly" reduce visibility for motorists Thursday evening and into Friday morning.

The watch covers Barrie, Orillia, Midland, parts of York, Durham, Halton and Peel regions, and most of Grey, Bruce, Dufferin and Lambton counties. The snow squall watch calls for possible snowfall accumulations of more than 15 cm in some areas.