Prime purpose of this lecture is to present on How do Clouds Form? Clouds Forms when water vapor in the air becomes liquid water or ice crystals. Simply, clouds develop out of the process of changing moisture from a gas to liquid. Fog is a cloud in contact with the ground. Cirrus is thin, feather like clouds that are made of ice crystals high in the atmosphere. Usually means a change in the weather is coming. Virtually all types of clouds and precipitation are due to rising air.