Snow Snow Snow refers to forms of ice crystals that precipitate from the atmosphere (usually from clouds) and undergo changes on the Earth's surface. It pertains to frozen crystalline water throughout its life cycle, starting when, under suitable conditions, the ice crystals form in the atmosphere, increase to millimeter size, precipitate and accumulate on surfaces, then metamorphose in place, and ultimately melt, slide or sublimate away. Snowstorms organize and develop by feeding on sources of atmospheric moisture and cold air. Snowflakes nucleate around particles in the atmosphere by attracting supercooled water droplets, which freeze in hexagonal-shaped crystals. Snowflakes take on a
Amorphous ice this likely the most common structure for HO in the universe at large. Just as there are many different crystalline forms of ice (currently 17+ known), there are also different forms of amorphous ice, distinguished principally by their densities. The production of amorphous ice hinges on the fast rate of cooling. Liquid water must be cooled to its glass transition temperature (about 136 K or −137 °C) in milliseconds to prevent the spontaneous nucleation of crystals. This is analogous to the production of ice cream from heterogeneous ingredients, which must also be frozen quickly to prevent the growth of crystals