A polar vortex is a low-pressure area—a wide expanse of swirling cold air—that is parked in polar regions. During winter, the polar vortex at the North Pole expands, sending cold air southward. This happens fairly regularly and is often associated with outbreaks of cold temperatures in the United States. Polar Vortex. It sounds like it could be some sort of alien death-ray or an extremely powerful washing machine, but what does it have to do with cold weather? A polar vortex is an area of low pressure—a wide expanse of swirling cold air—that is parked in polar regions. The one up north can cause some pretty wild weather and sub-zero temperatures in the United States. But it's not a new thing—this low-pressure system is almost always up there. Sometimes this low-pressure system, full of cold Arctic air, strays a little bit too far from home. Part of it can break off and migrate southward, bringing all of that cold air with it. Just like that, areas as far south as Florida get to experience their own little taste of life in the Arctic.