Haines Index is used to indicate the potential for rapid fire growth due to dry and unstable atmospheric conditions over a fire area. The index is a simple way to measure the atmosphere’s contribution to the fire’s growth potential. A high Haines Index is correlated with large fire growth where winds do not dominate fire behavior.
During days with a high Haines index and a Lightning Activity Level (LAL) above 4, fire behavior can become very erratic, unpredictable and difficult for resources to control and contain.
2014 Incident Response Pocket Guide, Page 65