Don't let the blue skies fool you, Toronto. The city has issued an Extreme Cold Weather Alert for Thursday ahead of a vicious cold snap that will set the scene for significant snowfall this weekend.

Dr. Eileen de Villa, Toronto's Medical Officer of Health, issued the Extreme Cold Weather Alert Thursday morning and it will remain in effect across the city until further notice. Alerts such as this are issued when the temperature in the daily forecast is expected to reach approximately -15ºC or colder, or when the wind chill is forecast to reach -20ºC or colder.

Other weather-related factors are considered when issuing Extreme Cold Weather Alerts, such as the looming snowstorm that's forecast to hit Toronto on Saturday.

Environment Canada says temperatures are expected to drop to a low of -12 CºC in Toronto on Thursday night, with a wind chill of -19ºC and flurries expected.

READ: Toronto Could Be Hit With Up to 20 cm of Snow This Weekend

Heading into the weekend, temperatures will remain frigid on Friday as a Colorado low tracks into Southern Ontario, bringing with it what The Weather Network has called "the coldest air we've seen so far in 2020." The Weather Network meteorologist Dr. Doug Gillham says daytime highs on Friday will run closer to 10 degrees below average.

By Saturday morning, Toronto should be experiencing what The Weather Network is calling the most significant snow event of the season to date, with up to 20 cm of accumulation forecast between Saturday and Sunday.

Behind the storm system, arctic air will plunge into the region, staying colder for the start of next week as well, according to The Weather Network.

"Sunday will be blustery and cold with blowing snow and bands of lake effect snow squalls southeast of Lake Huron and Georgian Bay," added Gillham.

The city says exposure to cold weather can be harmful to your health and is reminding the public that extreme weather poses a serious threat to vulnerable residents, including people experiencing homelessness or are under-housed, those who work outdoors, people with a pre-existing heart condition or respiratory illness, elderly people, infants, and young people.

The city is also asking that residents help vulnerable people by calling 311 if there is a need for street outreach assistance, or to call 911 if the situation is an emergency.

During an Extreme Cold Weather Alert, members of the public are encouraged to take the following precautions:

  • Check the weather report before going outside.
  • Dress in layers, making sure your outer layer is windproof, and cover exposed skin.
  • Wear a hat, warm mittens or gloves, and warm boots.
  • Stay dry. Your risk of hypothermia is much greater if you are wet.
  • Choose wool or synthetic fabrics for your clothes instead of cotton, because cotton absorbs and holds moisture, no longer keeping the wearer warm.
  • Seek shelter if you normally spend long periods outside. Depending on the wind chill, exposed skin can freeze in minutes.
  • Drink warm fluids other than alcohol.
  • Warm up by taking regular breaks in heated buildings when enjoying winter activities outside.
  • Consider rescheduling outdoor activities, or limiting time outdoors, during colder temperatures, especially if it's windy.
  • Heat your home to at least 21 degrees Celsius if infants or elderly people are present.
  • Call or visit vulnerable friends, neighbours and family to ensure they are not experiencing any difficulties related to the weather.