When ice crystals in a cloud grow large enough to fall and the air remains cold all the way to the ground, the result is snow. Each snowflake is a unique aggregate of ice crystals, often hexagonal in form.

Snow requires both moisture and temperatures low enough to keep the crystals from melting. The intensity can range from light flurries to heavy snow that accumulates several inches per hour. Wind can redistribute snow into deep drifts even after the precipitation ends.

Snowpack stores water that is released gradually during spring melt, supplying rivers and reservoirs. Heavy snow disrupts transportation and can collapse roofs, yet it also creates recreational opportunities and insulates the ground. Measuring snow water equivalent is as important as measuring depth for water-resource management.

• Ice crystals falling as precipitation
• Requires cold temperatures to the surface
• Accumulates and can be blown into drifts
• Important for water storage