Cumulus clouds are one of the three basic cloud types. They are low
clouds that develop in a vertical direction, beginning with the base. The base
of the cloud is often no more than 3,000 feet above the ground, but
the top often varies in height. Small, separate cumulus clouds usually
mean fair weather, but with additional heating from the earth's surface,
they can grow vertically throughout the day. The top of such a cloud can
easily reach 20,000 or more into the troposphere. These clouds can develop
into larger clouds, which are called towering cumulus. Towering cumulus may produce rain showers. Further development of towering cumulus may create a cumulonimbus and thunderstorms.