The breaking off of part of the vortex is what defines a polar vortex event. But it actually occurs when the vortex is weaker, not stronger. That might sound weird—but it actually makes sense. Normally, when the vortex is strong and healthy, it helps keep a current of air known as the jet stream traveling around the globe in a pretty circular path. This current keeps the cold air up north and the warm air down south. But without that strong low-pressure system, the jet stream doesn’t have much to keep it in line. It becomes wavy and rambling. Put a couple of areas of high-pressure systems in its way, and all of a sudden you have a river of cold air being pushed down south along with the rest of the polar vortex system. It's important to remember that not all cold weather is the result of the polar vortex. While the polar vortex is always hanging out up north, it normally minds its own business. It takes pretty unusual conditions for it to weaken or for it to migrate far south, and other things can cause cold arctic air to travel our way, too. 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.