TORONTO -- The extended bout of unseasonably mild weather in Toronto is now over as frigid temperatures arrive in the city on Wednesday.

The city’s top doctor has now issued an extreme cold weather alert for Toronto, which is expected to feel like -12 this morning with the wind chill.

Environment Canada says the temperature is expected to drop to -12 C later tonight and will feel closer to -18.

Extreme cold weather alerts are typically issued when the daily forecast suggests temperatures will reach approximately -15 C or colder, or when the wind chill is forecast to reach -20 or colder.

An #ExtremeColdWeatherAlert has been issued for Toronto today. More info here: https://t.co/SzXX3p55qw — Toronto Public Health (@TOPublicHealth) January 29, 2020

Other weather-related factors can also be considered when deciding if an extreme cold weather alert should be issued, the city says.

In addition to year-round 24-hour respite sites already open across Toronto, a warming centre will be open at Metro Hall starting tonight at 7 p.m. and will remain open until noon on the day the alert is terminated.

The city will also offer additional overnight street outreach and transit tokens at some drop-ins while the alert is in effect.

The city’s medical officer of health is urging members of the public to check on vulnerable family members, friends, and neighbours.

Those at the greatest risk of cold-related illnesses are people experiencing homelessness, those who work outdoors, elderly people, infants, and those with pre-existing heart of respiratory conditions.

Members of the public are advised to dress in layers and stay dry, drink warm fluids, and reduce the amount of time spent outdoors.