What Is Snow?
Snow is a type of frozen precipitation that forms when water vapour in the atmosphere freezes into ice crystals. These crystals grow inside clouds and can combine with other crystals before falling toward the ground.
Individual ice crystals often join together to form snowflakes. Their size, shape, and moisture content can vary considerably depending on the temperature and humidity in the atmosphere.
Snow can fall lightly for a short period or become part of a prolonged heavy snowfall event. Wind can also redistribute snow after it reaches the ground, producing conditions such as blowing snow, snowdrifts, and reduced visibility.
Related Conditions
| Condition | Description |
|---|---|
| Heavy Snowfall | Snowfall that produces a significant accumulation of snow over a relatively short period. |
| Blowing Snow | Snow lifted from the ground and carried by the wind, potentially reducing visibility. |
| Snowdrift | A mound or accumulation of snow formed as wind deposits snow in particular areas. |
| Snow Squall | A localized burst of heavy snow that can cause sudden reductions in visibility and rapid accumulation. |
| Whiteout | A condition in which snow, cloud cover, or blowing snow makes the horizon and surrounding features difficult or impossible to distinguish. |
Related Alerts
| Alert | Description |
|---|---|
| Snowfall Warning | Issued when significant snowfall is expected to meet warning criteria for the affected region. |
| Snow Squall Warning | Warns of snow squalls capable of producing hazardous travel conditions, including sudden near-zero visibility. |
| Winter Storm Warning | Issued when a significant combination of hazardous winter weather is expected. |
| Blizzard Warning | Warns of severe winter conditions involving strong winds, blowing snow and very poor visibility. |
| Blowing Snow Advisory | Issued when blowing snow is expected to significantly reduce visibility and create hazardous conditions. |
What Causes Snow?
Snow forms when there is enough moisture in the air and temperatures inside a cloud are cold enough for ice crystals to develop. Water vapour freezes onto tiny particles in the atmosphere, allowing the crystals to grow.
As the crystals get larger, they can stick together and form snowflakes. Eventually, they become heavy enough to fall from the cloud.
Whether those snowflakes actually reach the ground as snow depends on the temperature of the air below the cloud. If the air stays cold enough, they remain frozen. If they pass through a deep layer of warmer air, they can melt and fall as rain.
Temperature also affects the type of snow that reaches the ground. Snow near the freezing point is often wetter and heavier, while colder temperatures generally produce lighter, drier snow.
Meteorologists look at temperature, moisture, storm tracks, radar and weather models to determine when and where snow may develop. Read How Do Meteorologists Predict Snow? to learn more about how snowfall forecasts are made.
FAQ
Snow forms in parts of the atmosphere where temperatures are below freezing. The temperature at ground level does not always have to be below 0°C for snow to fall.
Yes. Snow can reach the ground when temperatures are slightly above freezing, especially if the warmer layer of air near the surface is shallow.
Snow is more likely to stick when the ground is cold and snowfall is heavy enough to overcome melting. Pavement, soil, grass and other surfaces can also cool at different rates.
Snow that falls when temperatures are close to 0°C is usually wetter and heavier. Colder conditions tend to produce lighter, drier snow.
Snow is the precipitation itself. A snow squall is a short, intense period of snow that can cause visibility and road conditions to change very quickly.
Snow falls from clouds. Blowing snow is snow that has already fallen and is lifted back into the air by wind.
No. Snow may melt when it reaches warmer ground, especially during light snowfall or when temperatures are above freezing.