The National Fire-Danger Rating System (NFDRS), implemented in 1972, was revised during a 3-year project (1975 to 1978) and reissued as the 1978 NFDRS. This report describes the developmental history of the NFDRS and its technical foundation. Detailed information is provided on modeling forest fuels and fuel moisture, and on development of the NFDRS components and indexes. The report presents equations used in the 1978 NFDRS and an extensive bibliography.

Methods are presented for analysing the relationship between fire danger rating indexes and fire activity as a means of evaluating the performance of fire danger rating systems. Percentile analysis is used to examine the data itself; logistic regression provides a means for statistical analysis. Ranking of selected items indicates indexes that deserve further assessment using subjective considerations. Methods rely on generally available data: the fire danger index for every day in the fire season, fire discovery date, and final fire size. For logistic regression analysis, the independent variable is the index, and dependent variables are fire-day, large-fire-day, and multiple-fire-day. Data analysis methods have been incorporated into the FireFamily Plus computer program for easy application. Potential uses of the analysis include choosing the most appropriate fire danger index and fuel model for an area, evaluating proposed changes to a fire danger rating system, and assessing the performance of a system in a location other than that for which it was designed. As a demonstration, this technique was applied to evaluation of several indexes and fuel models of the U.S. National Fire Danger Rating System on the Tonto National Forest in Arizona, USA, using fire and weather data for 1974–2001.

This study presents spatially and temporally resolved measurements of air temperatures and radiant energy fluxes in a boreal forest crown fire. Measurements were collected 3.1, 6.2, 9.2, 12.3, and 13.8 m above the ground surface. Peak air temperatures exceeded 1330 °C, and maximum radiant energy fluxes occurred in the upper third of the forest stand and reached 290 kW·m–2. Average radiant flux from the flames across all experiments was found to be approximately 200 kW·m–2. Measured temperatures showed some variation with vertical height in the canopy. Equivalent radiometric temperatures calculated from radiant heat flux measurements exceeded thermocouple-based temperatures for all but the 10-m height, indicating that fire intensity estimates based on thermocouple measurements alone may result in underestimation of actual radiant intensity. The data indicate that the radiative energy penetration distance is significantly longer in the forest canopy than in the lower levels of the forest stand.

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