Cold weather alerts for the cities of Toronto and Hamilton remain in effect today after temperatures plummeted overnight.

Toronto’s Chief Medical Officer of Health and Hamilton's Medical Officer of Health issue both issued cold weather alerts on Sunday ahead of frigid overnight temperatures.

A high of -11 C is expected in the city today and Environment Canada says Toronto could see a low of -15 C on Monday night.

During the extreme cold, residents are being warned to bundle up and avoid prolonged exsposure to the elements.

“There are two main things that we are considered about with the cold. . One is hypothermia, where the body’s temperature actually drops below 35 C and then you can also get actual freezing of the body tissue which we call frost bite,” Associate Medical Officer of Health Dr. Howard Shapiro told CP24 on Monday morning. “The main thing is to dress appropriately, to be able to take breaks so you can warm up and also to be aware of the signs or symptoms of frostbite or hypothermia.”

Pat Anderson, manager of Shelter, Support and Housing Administration with the City of Toronto, says that starting this year, the city will keep warming centres open 24 hours in January and February regardless of whether a cold weather alert has been issued.

"In the shoulder seasons, when an alert is called, they are open 24 hours as well," she said. 

Staff at 20 drop-in centres across the city will also distribute tokens during cold weather alerts and additional beds are made available.

The weather should return to more seasonable temperatures on Tuesday.

Environment Canada is calling for a high of -3 C on Tuesday, a high of 0 C on Wednesday and a high of 1 C on Thursday.