Fire danger rating in the United States of America: an evolution since 1916*

Abstract

Fire scientists in the United States began exploring the relationships of fire-danger and hazard with weather, fuel moisture, and ignition probabilities as early as 1916. Many of the relationships identified then persist today in the form of our National Fire-Danger-Rating System. This paper traces the evolution of fire-danger rating in the United States, including discussions of significant developmental milestones, innovative instrumentation, and a succession of analogue fire-danger meters, or calculators. Although the primary theme of this paper is an historical review of pioneering efforts leading up to our current state-of-knowledge, a common thread throughout this paper is the desire by every generation of developer to achieve a ‘purely analytical system’. A national system was first introduced in 1964. The current system used throughout the USA was implemented in 1978, with optional revisions added in 1988. We present this evolution within the context of three periods of development: first, the pioneering efforts initiated at the Priest River Experiment Station in northern Idaho; second, the implementation of a national, standardised fire-danger-rating system; and third, spatially explicit delivery systems that provide a national view of weather and fire potential, which include national fire-danger and weather maps and satellite-derived maps that reflect the state of live vegetation across the United States.