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.

According to the National Weather Service, a polar vortex will impact most of the country this weekend, here is what you need to know.

A blast of Arctic air is set to cover much of the United States with temperatures below freezing starting on Friday and into next week, impacting millions of Americans in nearly all of the contiguous states.

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.

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.

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.