Cumulus clouds are white, puffy clouds that look like pieces of floating cotton. Cumulus clouds are often called "fair-weather clouds" The base of each clouds is flat and the top of each cloud has rounded towers. When the top of the cummulus clouds resemble the hrad of a cauliflower, it is called cummulus congest us or towering cumulus. These clouds grow up ward and they can develop into giant cumulonimbus clouds, which are thunderstorm clouds.