Environment Canada issued the warning Sunday morning, saying a “period of very cold wind chills is expected.”
The agency said wind chill values near -30 Celsius are possible Sunday evening and into Monday morning.
Environment Canada said the risks are greater for young children, older adults, people with chronic illnesses, those working or exercising outdoors and for those without proper shelter.
“Watch for cold-related symptoms: shortness of breath, chest pain, muscle pain and weakness, numbness and colour change in fingers and toes,” the warning reads.
The agency said to dress warmly, and in layers that can be removed if you get too warm.
“The outer layer should be wind-resistant,” Environment Canada said.
The agency also reminded residents that if it’s too cold for humans to stay outside, then “it’s too cold for your pet to stay outside.”