One of the nicest things about summer is a nearby afternoon thunderstorm. The storm bubbles up on the horizon and a few minutes later you get a nice gust of cool, refreshing wind. This gust of wind is called an "outflow boundary," and it's one of the most interesting weather phenomena there is.

A photographer caught this incredible picture of a shelf cloud in Starkville, Mississippi today. There are exactly two reactions to this kind of sky: 1) turn around in fear; or 2) take as many pictures as possible.