The type of cloud that is fluffy and white, often associated with fair weather, is called cumulus clouds. Cumulus clouds are typically characterized by their cotton-like appearance, with a flat base and a rounded, lumpy top. They form when warm, moist air rises and cools, causing water vapor to condense into tiny water droplets. Cumulus clouds can indicate good weather, especially when they are well-defined and not overly extensive. However, they can develop into larger storm clouds, such as cumulonimbus, if atmospheric conditions change. Observing cumulus clouds is a common pastime for weather enthusiasts and can be a sign of a pleasant day ahead.