Environment Canada said the vast majority of Ontario is under prolonged extreme cold warnings, with wind chill values in many areas hovering around -40 C.
The weather agency has issued extreme cold warnings for areas around Lake Huron and Georgian Bay stretching to the north.
Communities around Lake Huron and Georgian Bay will see cold weather continue into Wednesday, while areas on the shore of Lake Superior are expected to see frigid temperatures cease on Tuesday.
The weather agency has also issued a snow squall warning watch for Northern Huron County and surrounding areas, which is expected to bring 30 to 60 cm of snow until Wednesday.
The agency said extremely cold temperatures put everyone at risk and frostbite can develop within minutes on exposed skin, especially with the wind chill.
It said to check on older relatives, neighbours and friends and to keep pets indoors.