Snow forms when water vapor turns directly into ice without ever passing through a liquid state. This happens as water condenses around an ice crystal.
Snow can take the form of ice pellets or snow flakes. As snow falls to the ground, it often melts on the warm surface of the Earth. If the surface of the Earth is chilled sufficiently, snow begins to pile up, creating snow drifts. In some locations, such as mountains, these snow drifts can reach several feet or meters in depth.