What is the name of the cloud type associated with thunderstorms and heavy rain?

Cumulonimbus is the cloud type associated with thunderstorms and heavy rain.

A cumulonimbus cloud develops when warm, moist air rises rapidly through an unstable atmosphere. Strong upward currents can build a towering cloud that extends from a low base into the upper troposphere. Its top may spread into a flat anvil shape when it reaches a stable layer near the tropopause.

These clouds can produce lightning, thunder, intense rain, hail, strong wind gusts, and sometimes tornadoes. Not every cumulonimbus cloud produces every hazard, but aviation and weather services treat mature examples as significant threats.

The name combines Latin roots meaning “heap” and “rain.” Cumulonimbus is different from ordinary cumulus, which is usually smaller and fair-weather related, and from nimbostratus, which tends to produce widespread, steadier precipitation without the same towering convective structure.