Cumulonimbus clouds are large, towering clouds often associated with thunderstorms. They can reach great heights, sometimes extending up to 12 miles into the atmosphere. These clouds are characterized by their dense, vertical development and can produce heavy rain, lightning, and even hail. These clouds form when warm, moist air rises rapidly, cooling as it ascends. The top of a mature cumulonimbus cloud can spread out into an anvil shape, indicating strong updrafts. Cumulonimbus clouds are important in weather systems and can lead to severe weather events, making them a key focus for meteorologists studying thunderstorms and severe weather.