A blast of Arctic air is set to cover much of the United States with temperatures below freezing starting on Friday and into next week, impacting millions of Americans in nearly all of the contiguous states.

Despite a cold start to the day, most of the U.S. will experience seasonably mild temperatures on Thursday. However, dangerous changes are on the way as a polar vortex tightens its grip on the nation as sends temperatures tumbling below freezing starting this weekend.

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.

Intense snowy wintry weather in the US has been fuelled by activity of the polar vortex, slipping down to engulf large parts of the country. Early January's winter storm prompted seven states to declare states of emergency,

An arctic blast will send temperatures across the United States plummeting as bitterly cold air that originated in Siberia will arrive from Canada by week’s end, bringing with it dangerously cold wind chills for millions of Americans.