A polar vortex is slated to sweep most of the continental United States bringing a hazardous freeze to millions of Americans from the Deep South to the Northeast Saturday going into next week.

Snow and winds are likely to trigger flight cancellations and cause headaches for people traveling to DC for Inauguration Day.

How the Polar Vortex Can Bring Arctic Blasts to the U.S. Vast weather patterns can carry blasts of frigid air far from the polar regions—here’s how it works