The polar vortex is stirring up, bringing the earliest hints that the seasons are changing. When will Wisconsin see its first ...

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.

The polar vortex is a gigantic, circular area of cold air high up in the atmosphere that typically spins over the North Pole (as its name suggests).

In the winter months, bitterly cold outbreaks of Arctic air across the Midwest and the Northeast are tied to what is known as the "polar vortex." ...

The polar vortex is stirring up, bringing the earliest hints that the seasons are changing. What does that mean for Vermont?

The term polar vortex is one that we all became familiar with after last winter's persistent cold. But what is it? Meteorologist Matt Moore explains.

When the polar vortex is weak or "perturbed," the flow of air is weaker and meanders north and south (rather than west to east).

Sedona's energy vortexes beckon droves of spiritual seekers. But what is a vortex really — and is Sedona the only place to feel one?

The polar vortex can't be felt in the United States or anywhere on Earth. Brutally cold temperatures are heading to the Midwest and Northeast this week -- but don't mistake this for a polar vortex ...

But we're still getting asked this question: Just what is the polar vortex, and why is it bringing super-cold temperatures to so much of the U.S.? So here's another go at it.