Fire Weather Index

The Fire Weather Index (FWI) System, developed by the Canadian Forest Service, is a comprehensive weather-based fire danger rating system consisting of six component indices and an overall Fire Weather Index. It uses daily weather observations (temperature, relative humidity, wind speed, and precipitation) to estimate fine-fuel moisture, fire behavior, and risk. The FWI System is used operationally across Canada, many U.S. states, and internationally for fire management decisions and fire danger forecasting.