The coldest burst of Arctic air this season is coming to put an icy exclamation point on America's winter of repeated polar vortex invasions, meteorologists warn. And it will stay frozen there all next week.

Like much of the U.S., Wisconsinites woke up Tuesday morning to bitter cold conditions. Many schools and colleges throughout the Milwaukee area closed as the area braced for the dangerous freezing temperatures. But is Wisconsin in a polar vortex? And what is a polar vortex anyways? Here's what to know.

When the Polar Vortex is in a weakened state, a jet stream wobble sending polar air into the mid-latitudes becomes more likely.