Southern Huron County, Goderich, and Bluewater are under a yellow cold warning alert, with wind chill temperatures expected to reach a low of minus 25 to minus 30 degrees.
Environment Canada warned that extreme cold puts everyone at risk, adding that frostbite can occur within minutes.
Risk is higher for young children, older adults, people with chronic illnesses, people working or exercising outside, and people without proper shelter.
The alert is in effect overnight Sunday into Monday morning.
