snøfnugg

Snøfnugg, or snowflakes, are ice crystals that form in clouds when water vapor deposits directly into solid ice around a microscopic nucleus such as dust. As they grow and then descend through air with varying temperature and humidity, they acquire the distinctive sixfold symmetry of the ice crystal lattice. The process depends on ambient conditions in the cloud, and slight changes in temperature and humidity influence the final shape.

Snowflake shapes vary widely. Common forms include plates, columns, dendrites, and needles. Under humid conditions, intricate, branched dendritic crystals often form, while drier conditions tend to produce simpler plates or needles. The temperature range in which a snowflake grows also affects morphology, leading to a range of patterns observed in different winter conditions.

Most snowflakes are small, typically about 1 to 2 millimeters across, though some can reach several millimeters. No two snowflakes are exactly alike in their full detail, because each experiences a unique trajectory through air currents and microclimates during descent, yielding a highly varied set of growth environments.

Snowflakes melt when they reach warmer surfaces or air. They have long been of interest in meteorology and crystallography; in the 20th century, researchers such as Ukichiro Nakaya studied and even produced artificial snow crystals. Beyond science, snowflake shapes have influenced art and culture as symbols of winter and uniqueness.

See also: snow, ice crystal, crystal habit.