snjó

Snjó is a form of precipitation consisting of ice crystals that form in the atmosphere when water vapor freezes. Snowflakes develop as moist air cools and ice crystals crystallize around microscopic nuclei, then grow and cluster as they descend. The structure and appearance of snowflakes vary, but most exhibit hexagonal symmetry because of the ice lattice. Snow generally forms when air temperatures are at or below freezing, though the precise characteristics depend on temperature, humidity, and cloud conditions.

When snow accumulates on the ground, it creates a snow cover that changes with time under temperature and pressure. Fresh snow is typically light and powdery in very cold, dry air, while warmer, moister conditions produce wetter, denser snow. Through compaction and metamorphism, the snowpack develops into layered structures that can become firn and, with long burial, glacial ice in some regions. Snow can also sublimate directly to water vapor under very dry conditions.

Snow influences both climate and human activity. It increases surface albedo, insulates soil and rock, and stores freshwater that is released during melt, feeding rivers and recharging groundwater. In winter, snow affects transportation, infrastructure, and recreation, and heavy or wet snow can cause hazards such as avalanches or roof loads. Climate variability and change can alter snowfall patterns, season length, and snowpack stability in many areas.