The polar vortex is making a return to the forecast, but the counterintuitive weather feature is nothing to fear.

The polar vortex is a broad, fast ribbon of cold air that encapsulates the Arctic high in the stratosphere. Stable, it confines cold air near the North Pole. Unstable, it is rocked and stretched out ...

Summer may end on a cooler note for parts of the U.S., with meteorologists suggesting that a weakened polar vortex could usher in below-average temperatures as September begins. In contrast to earlier ...