An Etymological Dictionary of Astronomy and Astrophysics

A precipitation in the form of → ice crystals that falls from clouds when the air temperature is below 0 °C. Snow occurs when → water vapor in the → atmosphere forms directly into ice and completely bypasses the liquid stage of → precipitation. Once an ice crystal has formed, it absorbs up even more water vapor and freezes due to the surrounding atmosphere. The ice crystal then falls down to earth’s surface in the form of a → snow crystal, snow → pellet, or more commonly known as the → snowflake. In short, snow formation requires the following conditions: 1) → relative humidity ≥ 100%, 2) → temperature < 0 °C, 3) presence of → condensation nuclei, and 4) → supercooled droplets.

Etymology (EN): O.E. snaw “snow;” cf. O.S., O.H.G. sneo, O.Fris., M.L.G. sne, M.Du. snee, Du. sneeuw, Ger. Schnee, O.N. snjor, Goth. snaiws “snow;” PIE base *sneig^wh- “to snow, snow;” cf. Mid.Pers. snêx, snêxr “snow;”
Av. snaēg- “to snow,” snaēžaiti “snows;” Skt. snih- “wet;”
Gk. nipha “snowflake,” neiphei “snows;” L. nix (genitive nivis); O.Ir. snigid “snows;” Lith. sniegas; Rus. snieg’.

Etymology (PE): Barf “snow,” dialectal vafr “snow,” var,
from Mid.Pers. vafr “snow;” Av. vafra- in jaiwi.vafra- “with deep snow.”