Cities across the U.S. are bracing for cold temperatures as a polar vortex arrives, bringing temperatures down to much below normal for mid-to-late January. Parts of Utah are on the "very western fringe" of a cold front that will bring in air from the Arctic.

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

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,