Name a common indicator of extreme fire behavior.

Rapid fire spread or crown fires are considered a common indicator of extreme fire behavior because they signify that the fire is moving quickly and potentially out of control. When a fire spreads rapidly, it can consume large areas in a short period, making it particularly dangerous for firefighters and the structures they are trying to protect. Crown fires, which involve fire climbing into the tops of trees, can generate intense heat and create their own weather patterns, further exacerbating the situation.

Low humidity can contribute to fire behavior but does not directly indicate extreme conditions without considering other factors. Frequent rainfall typically mitigates fire risk, while steady wind flow could influence fire behavior but does not inherently indicate extreme behavior on its own. Rapid fire spread, along with crown fires, highlights serious fire conditions and necessitates an urgent and informed response from firefighting teams.