Extreme is the highest of five levels on the avalanche danger scale. Natural and human-triggered avalanches are certain; large to very large avalanches are expected in many areas; and all avalanche terrain should be avoided.
Extreme avalanche danger is used rarely in avalanche forecasts. It is employed when the likelihood and size of avalanches could present conditions that are outside the realm of many people’s experience. Conditions such as avalanches running beyond the existing bounds of their path, avalanches running into forested terrain, avalanches running across valleys and up the other side, or avalanches impacting simple terrain are possibilities under extreme danger.