Wicked winter weather conditions are threatening the health and wellness of warm-blooded Torontonians once again this week as very cold air moves back into Southern Ontario with a vengeance.

Toronto's Medical Officer of Health issued an extreme cold weather alert for the city this morning — the first since February 18 — based on information from Environment Canada suggesting that wind chill values will soon reach -20 C or colder.

It will feel like -18 C in Toronto for most of Monday, according to the federal weather agency, with wind gusts of up to 80 km/h.

This evening, however, temperatures are expected to drop down to -12 C with a wind chill of -20 C, making things dangerous for people experiencing homelessness or under-housing.

TO's Medical Officer of Health has issued an #ExtremeColdAlert today. More info: https://t.co/3hqeeMFovs #StayWarm

— Toronto Public Health (@TOPublicHealth) February 25, 2019

The City asks all residents to be on the lookout for those in need of street assistance (in which case they should call 311), and also to check on elderly or otherwise vulnerable friends and family members.

"Dress in layers, making sure your outer layer is windproof, and cover exposed skin," advises Toronto Public Health, among other recommendations.

"Seek shelter if you normally spend long periods outside. Depending on the wind chill, exposed skin can freeze in minutes."