Mammatus clouds are distinctive and striking cloud formations characterized by their pouch-like shapes hanging from the underside of a cloud, typically a thunderstorm anvil cloud but not exclusively. The name “mammatus” comes from the Latin word “mamma,” meaning “udder” or “breast,” reflecting the cloud’s bulbous appearance. These clouds are often associated with severe weather conditions and can appear before or after storms, but their presence alone does not necessarily indicate severe weather.

Mammatus clouds form when cold air within the cloud sinks down into warmer air beneath the cloud base. This process is the opposite of the more common cloud formation mechanism, where warm air rises. The sinking cold air causes the cloud to bulge downward, creating the distinctive pouches. The exact mechanisms behind the formation of mammatus clouds are complex and involve factors like temperature, moisture content, and the dynamics within the cloud.

These clouds can vary in appearance, ranging from soft and elongated lobes to more defined and rounded shapes. The color of mammatus clouds can also vary dramatically, from bright white when illuminated by the sun to dark and ominous shades when they are backlit or occurring during stormy conditions.

While mammatus clouds can be a mesmerizing sight, their association with severe weather conditions means that observing them should be done with caution, especially if they form in the vicinity of thunderstorms, which can produce heavy rain, strong winds, hail, and even tornadoes.