Physical constitution

(Section 2.3.9.7)

Cumulus is composed mainly of water droplets. When of great vertical extent, Cumulus may release precipitation in the form of showers of rain, snow or snow pellets.

Ice crystals may form in those parts of a Cumulus where the temperature is below 0 °C. The ice crystals grow at the expense of evaporating supercooled water droplets, transforming the cloud into Cumulonimbus. In cold weather, when the temperature in the entire cloud is well below 0 °C, this process leads to the degeneration of the cloud into diffuse trails of snow.