Most of southern Ontario is now under an extreme cold warning including Toronto and the GTA.
Environment Canada issuing the warning because wind chill values in the minus 30s are expected overnight Saturday and Sunday.
The agency says "A multi-day episode of very cold wind chills is expected."
The weather advisory adds, "2017 is about to end with the coldest air of the year. A fresh surge of record-breaking Arctic air is forecast to encompass the entire province in its icy grip. A trough of low pressure currently over Southern Ontario will drop south of the Great Lakes tonight, opening the door to an even colder northerly wind."
"Although winds will be relatively light, the extreme cold is expected to produce windchill values below minus 30 overnight into Sunday, and again Sunday night. New Years Eve revellers are cautioned that windchill values will be near minus 30 late Sunday evening as we ring in 2018."
Environment Canada says very cold conditions could continue into New Year's Day and Tuesday.
An extreme cold weather alert issued earlier this month by Toronto's medical officer of health remains in effect.