Lambton Public Health issued a Cold Weather Alert for the county late Monday afternoon based on Environment Canada's forecast low of -15C.
The alert, the first of the season, is in effect until temperatures climb above the threshold Tuesday.
All residents should take precautions by dressing in layers, shielding exposed areas from the wind like the head, neck and face and by limiting time spent outdoors.
Public health advises local agencies that provide shelter and assistance to the homeless to prepare for an increase in demand.
The coldest weather of the winter season has flooded into southern Ontario.
Environment Canada meteorologist Geoff Coulson says frigid Arctic air may require extreme cold warnings to be issued at times this week. The criteria for that is a wind chill of at least minus 30 C.
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Coulson says we'll near the extreme cold warning threshold again overnight Wednesday into Thursday morning.
There's also the likelihood of snow squalls at times this week to the southeast of the Great Lakes. The extreme portions of north and east Lambton County could be impacted at times.
