The polar vortex is expected to reach the Utah-Idaho border sometime in the late afternoon and evening Friday as it continues to move south. As it moves through parts of the state, it will produce small snow showers, bringing more snow to the region before drier conditions return.

Dangerous temperatures are sweeping the country, with 100 million people from the Plains to the Northeast feeling the chill. Even those in the South will see some effects. Several cities have already declared weather emergencies,

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

These severe cold events occur when the polar jet stream – the familiar jet stream of winter that runs along the boundary between Arctic and more temperate air – dips deeply southward, bringing the cold Arctic air to regions that don’t often experience it.

A disruption in the polar vortex is about to send an Arctic air mass from Siberia as far south as Florida. Yes, Siberia—and it’s as dramatic as it sounds. As many as 47 states will experience unseasonably cold temperatures. Some areas will be hit with dangerous wind chills as low as 40 below zero.

A major cold blast is in store for millions of Americans as a lobe of a polar vortex will bring brutally cold temperatures to nearly every American east of the Rockies.

The polar vortex is a ring of cold air that typically circles the Arctic. A strong jet stream essentially acts like a fence, keeping it locked there. If there's any weakening in the jet stream (the fence), the frigid air can become unstable and spill out. This sends the normally trapped cold air much farther south.

The polar vortex will extend into the metro St. Louis area Saturday bringing several days of temperatures plunging to single digits and wind chills below zero.

A polar vortex will plunge Colorado into bitter, sub-zero cold this weekend and could bring up to 10 inches of snow in some parts of the Denver metro, National Weather Service meteorologists say. We’ve rounded up all of our arctic cold coverage below,

A look at some of today's top trending headlines including the latest updates on the Gaza ceasefire deal, polar vortex and much more.

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.