As the U.S. prepares to take on another bout of cold weather, the term "polar vortex" is getting thrown around. But what is it?

Behind the historic winter storm that blasted 40 states this weekend, a dome of Arctic air associated with the polar vortex will bring days of life-threatening temperatures to much of the country, refreezing ice and snow,

Tens of millions of people are in the path of a major winter storm. Federal cuts threaten efforts to understand the causes of such weather.

"Potentially hundreds of thousands of people may go without electricity and heat for days, one meteorologist said

The worst of the sleet and ice should be over by Tuesday, but you can expect cold temperatures to hang around for the next several days.