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. Cumulonimbus clouds form when warm, moist air rises rapidly, cooling as it ascends. This process creates strong updrafts, leading to the formation of the cloud's anvil-shaped top. They are an important part of the water cycle and play a significant role in weather patterns, particularly in tropical and temperate regions.