Cumulus clouds are fluffy, white clouds that often look like cotton balls. They form when warm air rises and cools, causing water vapor to condense into tiny droplets. These clouds usually indicate fair weather, but they can develop into larger storm clouds if conditions change. Typically found at low to mid altitudes, cumulus clouds can vary in size and shape. They are part of the cloud classification system, which categorizes clouds based on their appearance and altitude. Cumulus clouds are commonly seen on sunny days and are a favorite subject for cloud watchers and photographers alike.