This is a photo of mammatus clouds, taken in Weld County, Colorado. Click on image for full size (72 Kb) Photo courtsey of Gregory Thompson

Mammatus clouds are pouches of clouds that hang underneath the base of a cloud. They are usually seen with cumulonimbus clouds that produce very strong storms.

Mammatus clouds are sometimes described as looking like a field of tennis balls or melons, or like female human breasts. In fact, the name "mammatus" comes from the Latin word mamma, or breast, because of this.