Fluffy Cumulus clouds are formed when bubbles of warm air rise form the Earth's surface. Water vapor the air cools and condenses (turns into liquid) forming clouds droplets. The clouds have a limited depth and are usually short-lived, lasting from 5 to 40 minutes. Sometimes, they develop into rain clouds. They are heapy clouds which form because of surface temperatures rising. When the temperatures rise, also more water (from pipes,etc.) evaporates into the atmosphere and cools off, forming a heapy mass of Cumulus. However, if it is very hot, cumulus clouds can develop even more, forming a Cumulonimbus, a very high storm cloud.