Interpreting the Canadian Forest Fire Weather Index (FWI) System

The Canadian Forest Fire Danger Rating System (CFFDRS) is the national system for rating fire danger in Canada. The Canadian Forest Fire Weather Index (FWI) System is a sub-system of the CFFDRS and has been in its present form since 1970, with the fourth version of the tables for the FWI System now being used (Canadian Forestry Service 1984; Van Wagner 1987). The purpose of the FWI System is to account for the effects of weather on forest fuels and forest fires. Other factors affecting fire danger (i.e., fuels, topography) are dealt with elsewhere in the CFFDRS.