Environment Canada issued extreme cold warning for parts of southern Alberta Friday.

A period of very cold wind chills is expected, making it feel like –40 C overnight and into Saturday morning.

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

The areas affected as of 1:56 p.m. Friday are:​

Kananaskis and Canmore

​Banff National Park

Airdrie, Cochrane, Olds and Sundre

Hanna, Coronation and Oyen

​Red Deer, Ponoka, Innisfail and Stettler

Environment Canada is reminding people to protect pets by limiting their time outdoors.

It's also warning some are at greater risk than others for frostbite and hypothermia including homeless people, infants and seniors, outdoor workers and people with certain medical conditions such as diabetes and diseases affecting the blood vessels.