MAMMATUS CLOUDS look like pouches hanging from the underside of a thundercloud.

They are rounded, smooth, sack-like protrusions hanging from the underside of a cloud (usually a thunderstorm anvil).

Mammatus clouds often accompany severe thunderstorms, but do not produce severe weather themselves. They occasionally accompany non-severe storms as well.

These cloud pockets develop when large droplets of water or ice fall into clear air as they evaporate.

Such pockets usually occur in turbulent air near a thunderstorm and are seen hanging below the anvil cloud.

Mammatus clouds often indicate severe weather, especially hail.