However, a deep freeze, thanks to the polar vortex dipping down from Siberia, is about to bring even harsher arctic blast to nearly 300 million Americans starting this weekend. Maps show where and when the cold front will arrive.

The coldest weather of the season to date will be due to a phenomenon called a polar vortex, an upper-level jet stream that typically circulates around both the North and South Poles, but can push cold winds down into the U.S. and Canada when it weakens and expands.