The City of Toronto remains under an extreme cold weather alert as periods of snow mixed with high winds gusting up to 50 kilometres per hour are expected to hit the GTA overnight.

A special weather statement for Toronto and much of southern Ontario also remains in effect as an "Alberta clipper" -- a fast-moving lower pressure system -- is expected to continue tracking through the region Sunday night, Environment Canada said in a statement.

The weather agency says up to 4 centimetres of snow could hit Toronto and the GTA by tonight, as temperatures fall to -11 C; a bitter wind chill could make it feel more like -25 C.

Officials are warning drivers to exercise extreme caution and avoid driving unless absolutely necessary.

"Weather conditions may change unexpectedly as a result of sudden storms and wind gusts causing reduced visibility. Driving defensively, reducing your speed and adjusting your following distance will assist in reaching your destination safely," the OPP said in a statement.

Treacherous weather conditions have caused several accidents across the province over the weekend, with the OPP responding to more than 1,600 crashes since Friday.

In the GTA, the OPP has responded to hundreds of collisions since Thursday. Officials are urging drivers to be prepared "in case something happens."

During an extreme cold weather alert, the city opens 26 shelter spaces for men and women. Street outreach workers will also be patrolling the downtown core to warn homeless people of the dangers of the cold, and to urge them to go to a shelter or another warm place.

The city calls an extreme weather alert when Environment Canada predicts overnight temperatures to plummet to -15 C or colder, a wind chill warning has been issued or extreme weather conditions are expected.