Extreme Fire Behavior 2

Weather - Fire Behavior
Page Last Modified / Reviewed: 
May 2020


Mild, moderate, and EXTREME fire behavior has always been present in cases of shelter deployment. It is critical for firefighters to maintain situational awareness of live and dead fuel moisture conditions, as well as predicted and current weather conditions. As fire behavior changes, it is critical to respond correctly to the changing situation.

Discuss how the following factors can contribute or lead to extreme fire behavior:

  • Frost Kill: Has there been a late or unusually extensive freeze? Is the loading of frost-killed fuels high?
  • Drought Conditions: Live Fuel Moistures Index, KBDI (Keetch-Byram Drought Index), Soil Moisture Index, low humidity, high temperatures.
  • Slope: increases fire spread uphill, preheats fuels by convection; may channel winds.
  • Sea Breeze/Foehn: wind direction may vary throughout the day, humidity changes may occur; strong wind velocities may drive fire behavior to extremes.

To aid situational awareness:

  • Track NFDRS (National Fire Danger Rating System) live and dead fuel moisture outputs.
  • Take hourly weather observations and track the hourly changes. By tracking fuel moisture and weather observations and using the Fire Severity Related to Fuel Moisture Chart, firefighters can be alerted to those conditions that can lead to situations where there is a high potential for extreme fire behavior.


Additional Resources

Incident Management Situation Report (IMSR)
Incident Response Pocket Guide (IRPG), PMS 461
NWCG Standards for Helicopter Operations, PMS 510
RT-130, Wildland Fire Safety Training Annual Refresher (WFSTAR)
Interagency Standards for Fire and Fire Aviation Operations (Red Book)
Wildland Fire Lessons Learned Center

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