Toronto's break from the extreme cold, which has blasted much of southern Ontario, will be short-lived with a cold snap beginning on Thursday.

Environment Canada has issued an extreme cold weather warning with a "prolonged period of very cold wind chills" for the City of Toronto and much of southern Ontario beginning Thursday afternoon and continuing through the weekend.

A statement from the agency says temperatures will fall rapidly this evening to reach lows of -20 C to -25 C with wind chill values making it feel like -35 to -40.

Temperatures and wind chill values will be slightly lower on Friday, but the extreme cold is expected to continue until Saturday and possibly into Sunday morning.

Environment Canada is warning people to cover up, check on older family members and neighbours and to not stay outside with pets.

For those travelling, wintry weather south of the border is impacting flight times. Dozens of flights have been cancelled at Pearson due to the weather in the U.S. East Coast.

Travellers are encouraged to check their flight status ahead of time.