The city's medical officer of health has issued an extreme cold weather alert for Toronto, with a frigid night ahead.

The alert comes with an overnight low of -17 C and a wind chill of -24 expected tonight.

Extreme cold weather alerts are issued when the temperature is forecast to reach approximately -15 C or colder, or when the wind chill is forecast to reach -20 or colder.

The alert activates additional shelter space for the city’s homeless population, as well as additional services, such as warming centres.

A warming centre will be open at Metro Hall today by 7 p.m.

Anyone who spots someone in need of street outreach is advised to call 311, the city says, or 911 if the situation is an emergency.

During an extreme cold weather alert, people are advised to dress warmly, stay dry, take breaks indoors to avoid extended periods outside, and to check on vulnerable neighbours, family members or friends.

The alert will be in effect until further notice from the city.

Daytime temperatures in the city are expected to be relatively warmer over the next few days. A daytime high of -3 C is expected Sunday, though it could feel closer to -12 with the wind chill.

A high of -6 C is expected on Monday, though it will feel closer to -13 with the wind chill in the afternoon.

This is the 24th extreme cold weather alert that the city has issued so far this year.