Cloud of the Day – Towering Cumulus Towering cumulus, also known as cumulus congestus, is what happens to fair weather cumulus if the atmosphere is more unstable. The stability of the atmosphere depends on several factors, such as the temperature gradient and the amount of water vapor in the air. When the temperature drops rapidly with height, the air is more inclined to boil up, and more water vapor means there’s more energy to help it. Where there is nothing to limit vertical development, rising air and moisture can build up into these robust towers. Identified by their substantial vertical size, which is often well over six thousand meters, and their patented “cauliflower” tops, these clouds are the big brothers in the cumulus family. Still no rain though, from towering cumulus. I know what Wikipedia says, but I think the definition of towering cumulus ends when precipitation starts.