The Toronto area began a descent into a deep-freeze Thursday night, making for a slippery commute Friday morning as slush turns to ice on GTA roads and streets.

Clearing skies gave way to plunging temperatures and rising winds, according to CBC Toronto meteorologist Jay Scotland.

"Temperatures will drop big time ... with wind-chill values around the -20 mark," Scotland says.

"You'll need your thicker winter jacket and be sure to cover up your extremities for the morning commute."

The city has issued an extreme cold weather alert — the 10th so far this year, compared to 32 by this same point in February last year — because of the plummeting temperatures.

The city issues such an alert whenever temperatures or wind-chill values drop below -15. 

Scotland says it should be fairly sunny Friday morning "but cold and a bit windy. Daytime highs will stay below seasonal and top out in the -2 C to -5 C range."