Get ready for another bout of downright frigid weather this week.

Environment Canada says the temperature is expected to drop to -12 with the wind chill tonight and even colder weather in on tap Thursday morning.

By about 7 a.m. Thursday, the temperature is expected to plummet to -19 with the wind chill.

The national weather agency’s chilly forecast prompted Toronto’s medical officer of health to issue an extreme cold weather alert Wednesday.

When an alert is triggered, the city offers additional cold weather-related services, including more shelter spaces for the homeless and overnight street outreach.

Toronto Public Health identifies people who are most at risk for cold-related illnesses as people who work outdoors, the homeless, the elderly, infants and young children, as well as people with pre-existing heart or respiratory conditions.

During an extreme cold weather alert, the city advises residents to:

• 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 stops keeping you warm once it gets wet.

• 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 21ºC 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.

Mild weather is expected to return to Toronto this weekend. The city will see a high of 8 C on Saturday and 5 C on Sunday.