Fire Danger Rating Systems

Fire danger describes how easy it is to ignite vegetation, how difficult a fire may be to control, and how much damage a fire may do. Fire danger rating systems produce qualitative and/or numeric indices of fire potential based on fuels, topography and weather. These rating systems allow fire managers to estimate present and future fire danger for a given area. They are commonly used as guides for initiating pre-suppression activities and selecting the appropriate level of initial response to a reported wildfire where detailed, site and time-specific information is unavailable. Usually these systems require mathematical descriptions of fuel models and their respective fuel properties as input.

The National Fire Danger Rating System (NFDRS), started in the 1960s, is the most commonly used system in the U.S. for rating fire danger. The NFDRS is a set of computer programs and algorithms that allow land management agencies to estimate present and future fire danger for a given area based on fuels, topography and weather. NFDRS characterizes fire danger by evaluating the upper limit of fire behavior in an area during a 24-hour period. Each day during the fire season, spot measurements of fire danger, calculated using the NFDRS at specific weather stations, are interpolated and mapped on a national basis by the Wildland Fire Assessment System (WFAS-MAPS) in Missoula, Montana. Two maps are produced daily during the fire season, an observed fire danger map and a forecasted fire danger map. The NFDRS outputs give relative ratings of the potential growth and behavior of any wildfire. Fire danger ratings are guides for initiating pre-suppression activities and selecting the appropriate level of initial response to a reported wildfire where detailed, site and time-specific information is unavailable. See: History of NFDRS.

The Oklahoma Fire Danger Model, operational since 1996, is a prototype next-generation model of the NFDRS. In contrast to the NFDRS, which uses one weather reading per day, the OFDM uses a real-time automated weather station network (the Oklahoma Mesonet) to provide fire danger ratings at a smaller resolution than the NFDRS.

The Canadian Forest Fire Danger Rating System (CFFDRS), under development since 1968, is a national system for rating the risk of forest fires in Canada. This system is made up of two subsystems–the Canadian Forest Fire Weather Index (FWI) System and the Canadian Forest Fire Behavior Prediction (FBP) System. Similar to the NFDRS, the Canadian system publishes daily maps of fire danger.