All of Southern Ontario is now under an extreme cold warning.
Environment Canada issued the warning at 11:05 a.m. Sunday.
Wind chill values near minus 30 are expected overnight thanks to a bitterly cold Arctic airmass.
Meanwhile, Sarnia-Lambton also remains under a snow squall warning.
It's expected to warm up slightly on Monday as the winds ease, but frosty temperatures near minus 20 or colder are still expected Monday night.
The agency says a milder air mass will begin to move in Tuesday.
People are being urged to limit their time outside and if it's necessary to go outside, bundle up and cover up any exposed skin as frostbite can develop within minutes.
It's recommended that pets come in from the cold as well.
