Major cities across the Northeast and Midwest are facing temperatures 10-20 degrees below average, according to forecasters.

A fresh blast of Arctic air is poised to spill across a wide swath of the United States, and the latest polar vortex map ...

The polar night jet, the high-altitude winter wind that circles the Arctic, acts like a flywheel for the cold season in the Northern Hemisphere. As climate change erodes the temperature contrast that ...