Freezing temperatures and icy roads were responsible for "nightmare" driving conditions on several roads and highways across southern Ontario Tuesday evening.

One of those involved 30 to 40 vehicles that slid into each other on the Highway 410 off ramp at Derry Road in Mississauga, where 15 people were sent to hospital with minor injuries.

"Most of them just slid into each other," Peel Paramedics superintendent Jeff Walsh told CBC News, saying the slippery conditions were to blame.

It's all thanks to a band of patchy freezing drizzle and light snow, Environment Canada said in a winter weather advisory for Toronto and surrounding areas.

Approximately 30 vehicles including tow trucks in collision on the offramp from Hwy 410 southbound to Derry Rd. Minor injuries. <a href="https://twitter.com/hashtag/onstorm?src=hash">#onstorm</a> <a href="https://t.co/h9QWlaSrGK">pic.twitter.com/h9QWlaSrGK</a> —@Media371

Ontario Provincial Police said there were more than 70 collisions in the Greater Toronto Area in just two and a half hours Tuesday.

Toronto Paramedics received multiple calls about collisions on Ontario highways especially, including one involving nine cars and two trucks on Highway 427 at Eglinton Avenue in Etobicoke.

Two cars collided head-on in a multi-vehicle crash in Toronto Tuesday evening on Highway 427. (CBC)

Ontario Provincial Police Sgt. Kerry Schmidt says Highways 401, 403, 427 and 410 are the hardest hit. No serious injuries have been reported but there have been several rollovers, Schmidt said.

Roads in <a href="https://twitter.com/hashtag/Brampton?src=hash">#Brampton</a> are extremely icy now Flash freeze has made the 410 highway an absolute drivers nightmare. Pls stay in if you can ^jc —@BramptonFireES

Multiple Collisions on the 410. Numerous City/Emergency agencies involved. PLEASE STAY OFF THE 410. <a href="https://twitter.com/hashtag/Brampton?src=hash">#Brampton</a> <a href="https://twitter.com/hashtag/mississauga?src=hash">#mississauga</a> <a href="https://twitter.com/BramptonFireES">@BramptonFireES</a> —@PeelPoliceMedia

"Just slow down. Don't be in a hurry. It might take you a little longer but it'll save you from getting into a crash," Schmidt advised.

The situation is no better in Peel Region, where police say there were 10 active collisions Tuesday evening and over 20 crashes since 3 p.m.

None have resulted in serious injuries, but Peel police are advising drivers to stay off the roads unless travel is necessary.

This vehicle in the ditch on Highway 410 in Brampton, Ont., was one of several that slid off the road. (CBC)

Anyone flying should check their flight status before heading out, Toronto's Pearson International Airport says.

Freezing rain causing slippery conditions around the airport. Check flight info with your airline & give yourself extra time on the roads. —@TorontoPearson

People involved in collisions should not leave their cars, Schmidt warns.

"Stay in your vehicle, do not get out ... A skating rink could result in cars, trucks, all kinds of vehicles sliding into you. We do not want to see pedestrians getting hit, getting hurt or getting killed."