With temperatures as low as 15°F, it seems unusual that parts of the south saw sleet and freezing rain instead of snow on Monday. Wintry precipitation isn't always determined by the temperature at the ground. Here's an explainer on how sleet and freezing rain can turn a beautiful snowfall into an icy death match.

This afternoon's satellite imagery shows an incredible slug of dry air moving across the south and east behind a cold front, bringing beautiful weather to millions of people. In fact, the air is so dry at 10,000 feet above sea level that its humidity is near zero percent in some spots.