As a storm bears down on Ontario on the busiest travel day of the year, motorists should be prepared for winter driving conditions that may become hazardous in some regions, police say.

In Toronto, a mix of rain and snow is expected Friday - the first day of the winter season - in addition to strong winds and a high of 4 C in the afternoon before the temperature drops to -1 C overnight. Snowfall accumulation in the GTA is expected to be about two centimetres.

To the north, however, communities are bracing for heavy snow and treacherous driving conditions, a day after the same storm walloped parts of the U.S.

According to Environment Canada, up to 25 centimetres of snow may fall within an area from Sault Ste. Marie and Timmins to Huntsville and Ottawa before the Colorado low moves further east Saturday. As the snow flies in that region, brisk winds will create near-whiteout conditions at times.

The traditional snow belt areas near Lake Huron and Georgian Bay should be prepared for heavy snow and snow squalls Friday night and Saturday as the storm moves across the Great Lakes, Environment Canada said.

Because of the storm, airlines are warning customers to check their flight status if they’re flying to cities affected by the low-pressure system.

Air Canada, for instance, issued advisories for travel to and from Chicago and Milwaukee in the U.S., and smaller airports in northern Ontario.

Busiest travel day at Pearson

The storm arrives on what is considered to be the busiest travel day of the year, as people depart for the holidays.

On Friday, more than 105,000 passengers are expected to pass through Pearson International Airport, Canada’s largest and busiest airport.

WestJet is flying 57,464 customers across its route network Friday, setting a new single-day record for passengers, according to the airline.

South of the border, travelers faced cancelled flights and closed roads after the storm dumped more than a foot of snow in parts of the Midwest.

In Chicago, more than 500 flights at its two airports were cancelled Thursday. Fewer cancellations were reported Friday.

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