Snowfall is precipitation that falls from clouds as snow, or the total amount of snow that accumulates during a storm or period of time. When meteorologists predict six inches of snowfall overnight, they mean that much snow will pile up on the ground before morning.

The word describes both the act of snow falling and the measurement of how much fell. A light snowfall might dust the ground with barely an inch, while a heavy snowfall could bury cars and close schools. Weather reports often track snowfall totals to help cities plan their response, whether they need a few plows clearing main roads or an army of trucks working around the clock.

Snowfall happens when water vapor high in the atmosphere freezes into ice crystals. These crystals clump together into snowflakes and drift down when they become heavy enough. The temperature, humidity, and wind all affect whether a snowfall produces light, fluffy powder perfect for skiing or heavy, wet snow ideal for packing into snowballs and building snowmen. Some mountains receive hundreds of inches of snowfall each winter, while many places never see snow at all.