The polar vortex of ultra-cold air usually spins around the North Pole, but it sometimes ventures south into the U.S., Europe and Asia. Some experts say such cold air outbreaks are happening more frequently, paradoxically, because of a warming world.

An area stretching from Texas to Tennessee braced Wednesday for the possible arrival of freezing rain and snow even as some parts of the U.S. hit by the plunging polar vortex this week began to shake off its icy effects.

An area stretching from Texas to Tennessee braced Wednesday for the expected arrival of freezing rain and snow, as some other parts of the country that already received an arctic blast this week prepared to go another round with the plunging polar vortex.

as some other parts of the country that already received an arctic blast this week prepared to go another round with the plunging polar vortex. Arkansas' capital, Little Rock, closed schools on ...

Arkansas’ capital, Little Rock, closed schools on Thursday ... with employees working remotely. The polar vortex of ultra-cold air usually spins around the North Pole, but it sometimes ventures ...

Snow is expected to taper off around Denver by the early afternoon, while temperatures will remain well-below freezing through Monday night.

DALLAS (AP) — A powerful winter storm brought heavy snow and icy conditions to parts of the U.S. South on Thursday, forcing officials to close schools, cancel flights and warn residents in some of the worst-hit areas to stay off roads as it lumbered eastward through Oklahoma and Texas.

Schools in several states will remain closed on Thursday after a winter storm brought over a foot of snow in some areas.

A huge swath of the U.S. was blasted with ice, snow and wind on Monday as the polar vortex that dipped south over the weekend kept much of the country east of the Rockies in

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.

things get a little chaotic. A weaker jet stream becomes wavy and unstable, like a loose rope in the wind. This instability allows cold Arctic air from the polar vortex to spill southward into ...

But during the winter, it is joined by a second atmospheric phenomenon dubbed the polar vortex. This swirl of frigid air, located more than 10 miles above Earth’s surface, strengthens each year ...