Another one of the types of solid water precipitation (see
Graupel), Rime is formed when supercooled clouds pass quickly over a mountain summit. This causes substantial deposits of ice feathers, formations that grow into the wind on most exposed objects as the cloud droplets freeze upon impact. The rime that is produced will vary in density and appearance, depending on temperature, wind velocity, cloud drop size and
turbulence.
Since rime is formed by the freezing of cloud droplets, their structure may be very grainy if the drops freeze instantly or very smooth if the cloud water has a chance to flow before it solidifies. Rime formed by flowing water often contains large crystals. The higher the wind and the larger the supercooled cloud droplets, the larger and more rapid rime formation. There are many forms of rime, ranging from icy to powdery, and including solid, granular and feathery. Rime structures up to a meter in length commonly form on trees and other objects on mountain summits.