vurtual:

Puffy patterns of mammatus clouds

Out of all the cloud types, only one kind derives from the Latin term for “udder”: Mammatus clouds. And when you see them, this meteorological name makes a whole lot of sense. They billow downwards in a pattern of distinctive lumpiness that peg them as fascinating subjects to photograph. Keep tuned in to weather reports for thunderstorms, because these puffy clouds usually indicate intense storms to come and you might find a rare opportunity to capture them.

Photos from Stormlover87, Jon Wisniewski, finepixtrix, Rodtas, and Alexander Photography.