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 typically indicate fair weather, but they can develop into larger storm clouds if conditions change. Cumulus clouds are usually seen in the daytime and can vary in size and shape. They are part of the cumulonimbus cloud family, which can produce thunderstorms. Observing cumulus clouds can help people predict the weather, as their appearance often signals stable atmospheric conditions.