Montreal is gearing up for the earliest snow-clearing operation in its history, with 15 to 20 centimetres of snow expected to fall overnight into Tuesday morning.

As of Monday night, Environment Canada issued a snowfall warning for:

Châteauguay - La Prairie area.

Laval area.

Longueuil - Varennes area.

Montréal Island area.

Montreal usually launches snow-clearing and removal operations on Dec. 17. The date of the earliest snow-removal operation in the ctiy's history was Nov. 19 — and that was 36 years ago, Mayor Valérie Plante said.

Plante offered her assurance that the city is doing all it can to minimize the impact of an early winter on pedestrian and vehicular traffic, as well as on public transit.

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"It was a surprise to read that there will be a lot of snow today," Plante said at a news conference on Monday. "But we are ready."

The city has been preparing for winter all year, the mayor said, and it will be launching a series of new initiatives in an effort to be proactive.

Those include more weather monitoring stations throughout the city, more abrasive-spreading trailers for slippery sidewalks, and more monitoring of the progress of snow-clearing and de-icing operations.

Are you ready for winter?

For 61 years, George Garage in Saint-Henri had a motto — it never turned customers away — until today.

"We're really totally, totally overwhelmed and everything, said the garage's owner, Rita Pazezanac. "We're actually in trouble a little bit, because we have too many people who want to change their snow tires."

Quebec moved up the deadline to install winter tires this year, from Dec. 15 to Dec. 1, which didn't help matters, she said.

Between the approaching deadline and the early snowfall, it means anyone who hasn't made an appointment at a Montreal-area garage to have their tires changed already may be in for a long wait.

There were about a dozen people waiting outside Pneu Gordons on Cavendish Boulevard just after 6 a.m. Monday, said manager Steven Kelly — and none of them had appointments.

View photos Matt D’Amours/CBC More

He said his business is booked up until after the Dec. 1 deadline.

Many people did make appointments a little earlier this year, Kelly said, but most of the employees at the garage had their winter tires on before Thanksgiving.

"There's a definitely a misconception that putting your winter tires on too early is going to ruin them. Definitely winter tires on your car in July aren't going to be healthy for the tire, but ... you can put your winters on in early October," he told CBC Montreal's Daybreak.