The polar vortex is splitting — an exceedingly rare phenomenon for this time of year that will be an unusual driver of warmer ...

Add Yahoo as a preferred source to see more of our stories on Google. A severe winter storm that brought freezing rain, sleet and snow to a large part of the U.S. was intensified by the polar vortex ...

The sudden blast may have come as a shock to many Americans after a mostly mild start to winter, but that warmth may have partly contributed to the ferocity of the storm. As atmospheric and climate ...