Snow happens when water high up in the sky freezes into tiny ice crystals and falls to the ground as solid precipitation. It needs air that is both cold enough and moist enough for these ice crystals to grow into snowflakes.
Basic conditions
Snow forms when the temperature in the cloud is at or below the freezing point, so water vapor can turn directly into ice instead of liquid droplets. At the same time, there must be enough water vapor in the air so that many ice crystals can grow.
How snowflakes form
Inside cold clouds, water vapor condenses onto tiny particles like dust, then freezes into microscopic ice crystals. These crystals stick together, becoming heavier snowflakes that eventually fall when gravity overcomes the upward air currents.
Why it is not just “frozen rain”
Snow is not rain that froze on the way down; it crystallizes directly as ice in the cloud. When temperatures are warmer in part of the cloud or lower in the atmosphere, the same system might produce rain, sleet, or freezing rain instead of pure snow.
Why some places get more snow
Areas that are both cold and moist, such as near large lakes, oceans, or mountains, tend to get more snow. In contrast, very cold but dry regions, or warm and humid regions, may see little or no snowfall because one of the key ingredients is missing.
