North American Public Avalanche Danger Scale

Avalanche danger is determined by the likelihood, size and distribution of avalanches.

Danger Level

Travel Advice

Likelihood of Avalanches

Avalanche Size and Distribution

Recommended Action in Developed Areas

Extreme Danger Level Avoid all avalanche terrain. Natural and human-triggered avalances certain. Large to very large avalanches in many areas. Being near or in avalanche terrain or avalanche zones is not recommended. Eliminate exposure to avalanche zones.
High Danger Level Very dangerous avalanche conditions. Travel in avalanche terrain NOT recommended. Natural avalanches likely; human-triggered avalanches very likely. Large avalanches in many areas; or very large avalanches in specific areas. Being in avalanche terrain or avalanche zones is not recommended. Minimize exposure time in avalanche zones. Monitor avalanche forecasts.
Considerable Danger Level Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential. Natural avalanches possible; human-triggered avalanches likely. Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. Be increasingly cautious in or under steeper terrain and in avalanche zones. Monitor avalanche forecasts.
Moderate Danger Level Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Natural avalanches unlikely; human-triggered avalanches possible. Small avalanches in specific areas; or large avalanches in isolated areas. Use caution in or under steeper terrain and in avalanche zones.
Low Danger Level Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Natural and human-triggered avalanches unlikely. Small avalanches in isolated areas or extreme terrain. Normal caution is advised.

Safe backcountry travel requires training and experience. You control your own risk by choosing where, when and how you travel.


Avalanche Size Definitions

Size

Description

Typical Mass

Typical Length

Typical Impact Pressure

1 Relatively Harmless > 10 tons 10 meters 1 kPa
2 Could bury, injure or kill a person 100 tons 100 meters 10 kPa
3 Could bury a car, destroy a small building, or break trees 1,000 tons 1,000 meters 100 kPa
4 Could destroy a rail car 10,000 tons 2,000 meters 500 kPa
5 Largest known 100,000 tons 3,000 meters 1000 kPa