The city of Toronto is under an extreme cold weather alert, as temperatures are forecast to plunge to -18 C overnight, feeling like -27 with the wind chill.

The city's medical officer of health, Dr. David McKeown issued the alert early Wednesday morning.

The alert triggers cold weather services for the homeless, including three 24-hour drop in shelters, additional shelter beds, increased street outreach and TTC tokens to get the homeless to shelter.

During extreme cold weather, Toronto residents are encouraged to call or check on vulnerable friends, neighbours and family members to see that they're not experiencing any difficulties related to the weather.

Wednesday's alert comes hours after the city was hit with snow and freezing rain, causing power outages across the city Tuesday night and into Wednesday morning.