growing weaker in the summer and strengthening in the winter. During winter in the Northern Hemisphere, the polar vortex often expands, pushing cold air southward along with the jet stream.

The polar vortex is a large area of low pressure, cold air around the Earth's poles that blows westward during the winter and eastward during the summer. A polar vortex collapse occurs when air in ...

As the impending summer forecast shows scorching heat, it's the perfect time to think about slipping away to a destination with milder temperatures, fresh mountain air and reasonable prices.

An arctic air mass is set to sweep ... area can expect to see "dangerously cold" temperatures starting on Wednesday night with subzero wind chills during the day. The coldest day predicted for ...