 Have you ever spent an afternoon looking up at the clouds trying to distinguish shapes like an elephant or a house? The clouds that you are most likely viewing are cumulus clouds. These clouds are usually easily distinguished because they look like puffs of cotton floating through the sky. Another good way to tell these clouds from others is that their lower portions are usually flat and fairly close to the ground, often only a little over 3,000 feet. When cumulus clouds are not very tall, they are good indicators of fair weather. However, when they rise vertically for many thousands of feet, it can be a sign of impending bad weather. Eventually you may see the top of a cumulus cloud start to grow rounded towers and turn into what is called cumulus congestus clouds, or towering cumulus. As cumulus congestus clouds continue to ascend, they can develop into cumulonimbus clouds, which are most often referred to as thunderstorm clouds. Thunderstorm clouds are easily identified by their dark bases that may be no more than 1,000 feet above the Earth's surface. Remarkable amounts of energy can be released by the condensation of water vapor within a cumulonimbus cloud, resulting in lightning, thunder, and even violent tornadoes. Hopefully you have a new appreciation for cumulus clouds, aside from the shapes that you can find. For University of Wyoming Extension, this is Glenn Owings, Exploring the Nature of Wyoming.