An Arctic blast that began in the northern plains on Saturday spread bitter cold from the Rockies through the East Coast and as far south as Florida by Tuesday morning. A blizzard warning was in effect for southern Louisiana, the furthest south such a warning has ever been posted.

A polar vortex dipping down from Siberia is bringing a cold front with frigid temperatures to millions 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.