Cumulus clouds are large, fluffy clouds that are commonly seen on sunny days. They are formed when warm air rises, cools, and condenses into visible water droplets or ice crystals. Cumulus clouds come in many shapes and sizes, ranging from small, isolated clouds to large, towering ones that can produce thunderstorms. They are usually found at low to mid-level altitudes in the atmosphere and can be an indicator of changes in weather patterns. Cumulus clouds play an important role in the Earth's