Snow and winds are likely to disrupt traffic, trigger flight cancellations, and cause headaches for people traveling to D.C. for Inauguration Day. Baby, it’s cold outside, and it’s about to get even colder for much of the United States.

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.

Most of the U.S. will enjoy milder temperatures on Thursday, but the warmup will be brief as a polar vortex will send temperatures tumbling below freezing for most of the nation starting this weekend.