As the polar vortex begins to retreat, the region will see a gradual return to typical winter conditions. Long-range forecasts suggest the coldest air will move out by mid- to late-January, according to the Climate Prediction Center at NOAA.

Temperatures plunged into the teens and single digits in some spots, and the snow-dusted winds are driving the wind chill below zero. The polar vortex, a swirling mass of Arctic air typically contained over the North Pole, has pushed south, driving bone-chilling temperatures into the eastern United States.

The polar vortex is a low-pressure system of cold air that swirls above Earth’s poles. There’s one over the South Pole in Antarctica – but for this story, we’ll be focusing on the one above the North Pole. Over the North Pole, the wind flows counterclockwise in the stratosphere around 16 to 50 kilometers (10-30 miles) high.

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.

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.