A polar vortex dipping down from Siberia will bring a cold front with frigid temperatures to nearly 300 million Americans. See maps of the arctic blast.

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.

A potent surge of Arctic air starts settling in Monday evening as a massive dip in the jet stream pulls in frigid air across the entire eastern half of the country. Temperatures are set to drop as low as 20 degrees below average through Thursday with the highs only reaching the teens and some lows even plunging below zero.