SUDBURY -- Environment Canada has issued extreme cold weather warnings for several communities in northeastern Ontario.

Communities include Timmins, Little Abitibi, Kesagami Lake, Cochrane, Iroquois Falls, Kirkland Lake, Englehart, Fraserdale, Pledger Lake, Kapuskasing, Hearst, Smooth Rock Falls, Chapleau, Missinaibi Lake, Gogama and Foleyet.

"A multi-day episode of very cold wind chills is expected," Environment Canada said in a news release Thursday.

"Wind chill values will improve this afternoon but are expected to drop to -40 again tonight into Friday morning. The extreme cold may continue into the weekend with wind chill values approaching -40 each night."

Extreme cold warnings are issued when very cold temperatures or wind chill creates an elevated risk to health such as frostbite and hypothermia.

Risks are greater for young children, older adults, people with chronic illnesses, people working or exercising outdoors, and those without proper shelter.

"Dress warmly," the release said. "Dress in layers that you can remove if you get too warm. The outer layer should be wind resistant."

Frostbite can develop within minutes on exposed skin, especially with wind chill. If it's too cold for you to stay outside, it's too cold for your pet to stay outside.