Police are reminding drivers to slow down as the GTA faces its first significant snowfall of the season.

Speaking to CP24 on Tuesday morning, OPP Sgt. Kerry Schmidt said in the overnight hours, police responded to 10 jack-knifed tractor-trailers across the region, including one incident in the westbound express lanes of Highway 401 at Victoria Park.

Schmidt said speed was a factor in many of the collisions that have been reported this morning.

“It really is messy out there. Traffic continues to build but everytime we have another jack-knife, another collision, we have a few lanes blocked, we lose some of that capacity and if traffic isn’t slow enough, that makes it even slower and even more frustrating knowing that these crashes are preventable,” Schmidt said.

Const. Clint Stibbe, with the Toronto Police Service's traffic services unit, said in the city, there was a number of single-vehicle collisions reported this morning.

“We are seeing quite a bit of snow coverage on (the off-ramps) and individuals are coming in way too fast, expecting those off-ramps are going to be fine. The reality is, by the time you realize they are not, it’s too late,” Stibbe said.

Stibbe cautioned drivers to slow down during their commute.

“I did see… a number of people travelling well over 100 kilometres per hour. That’s the speed limit on a dry day and these individuals are doing it on snow-covered lanes and at distances away from cars of a few metres,” he said.

“Everybody needs to just slow down. It’s not worth it. Running on the expressways so quickly, you are putting yourself and others in danger.”

The city of Toronto's winter operations department said salters were out overnight and plowing operations continued through the morning rush hour.

"We started last night at about 4 p.m. with salting. We salted all night and at around 3 a.m. this morning we started arterial road plowing. We’ve been at that hard. The crews have been working very hard overnight and now we are focusing on sidewalks as well," Myles Currie, the director of the city's Transportation Services department, said Tuesday. 

"We’ve seen varying amounts of snow in different parts of the city and we are responding accordingly."

Toronto and much of southern Ontario was under a special weather statement on Tuesday morning and Environment Canada says snowfall amounts of between eight and 10 centimetres were reported overnight.

The snow is expected to taper off Tuesday as frigid temperatures roll into the city.

The city's medical officer of health issued an Extreme Cold Weather Alert on Tuesday morning. The temperature in Toronto is expected to drop to -19 with the wind chill overnight.