Toronto is about to be hit by the coldest blast of arctic air it's seen this year so far, according to meteorologists, making temperatures uncomfortably low as we're simultaneously walloped with snow.

Dr. Eileen de Villa, Toronto's Medical Officer of Health, just issued an Extreme Cold Weather Alert that will remain in effect across the city until further notice.

Such alerts are always issued when Environment Canada forecasts temperatures of -15 C or lower, or when the wind chill is expected to make it feel like less than -20 C outdoors.

Other weather-related factors — such as the massive snow storm headed our way — can factor into Toronto Public Health's decision regarding whether or not to issue an alert.

Toronto's Medical Officer of Health has issued an Extreme Cold Weather Alert today for Toronto in anticipation of colder weather conditions. The alert activates local services supporting vulnerable residents. #CityofTO news rel: https://t.co/U8xiIW4484

— City of Toronto (@cityoftoronto) January 16, 2020

Environment Canada is calling for a low of -12 C in Toronto on Thursday night, with a wind chill of - 19 C and flurries expected.

Temperatures will remain frigid on Friday as a Colorado low tracks into Southern Ontario, bringing with it what the Weather Network calls "the coldest air we've seen so far in 2020." 

By Saturday morning, Toronto should be experiencing its most significant snow event of the season to date with as much as 20 cm of accumulation forecast between Saturday and Sunday.

Unreal. And a snowstorm on Saturday. Freezing temps and snow across Canada by the looks of it. To be honest, we’ve had it good lately. Things were bound to take a turn. #Toronto https://t.co/7gXXmOqQqz

— Michelle Jones (@maej43) January 16, 2020

"Exposure to cold weather can be harmful to your health," reads the alert issued by de Villa for Toronto on Thursday morning. 

"Those most at risk of cold-related illness are people experiencing homelessness or those under-housed, those who work outdoors, people with a pre-existing heart condition or respiratory illness, elderly people, infants and young children."

Toronto Public Health is advising members of the public to take appropriate cold weather precautions, such as bundling up, staying dry and avoiding the outdoors.

Those with vulnerable friends, neighbours and family members are asked to check on their loved ones "to ensure they are not experiencing any difficulties related to the weather."