Environment Canada issued an extreme cold warning for the Kingston, Napanee and Picton regions.
Overnight temperatures between Friday and Saturday are expected to fall to nearly -30 C.
The weather agency says temperatures should warm a little by Saturday morning.
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Environment Canada says you should watch for cold-related symptoms such as shortness of breath, chest pain, muscle pain or weakness, numbness and colour change in fingers and toes.
Dress warmly and in layers, it says, adding that the outer layer should be wind resistant.
Environment Canada says that if it’s too cold for you to be outside, it’s too cold for your pets too.