Unless precipitation is considered, no sound basis is available either for rating the relative difficulty of a fire season or for judging comparative accomplishments in fire control from year to year. This article describes the development and use of a single index of precipitation conditions for the counrty as a whole. It also points out the necessity of considering the effect of surpluses or deficiencies in precipitation over extended periods in gauging the degree of fire danger, rather than being influenced in this respect solely by current or short term weather conditions. For general index purposes it is held that cumulative weather records will serve this purpose fairly well, but for local and more accurate gauges of this factor research has yet to produce a satisfactory measuring device.