How well does the growing season index correspond to the start of fire season?

Fire season is often identified by specific calendar start and end days. In any given year, the actual start of the season - as determined by fire activity - typically differs from that calendar day due to the prevailing temperature, humidity, wind, and snow pack conditions. A reliable association between a climate-based annual index and actual fire occurrence would be of use for current, as well as past and future climate, estimates of fire season. We used the North American Regional Reanalysis historic data set, and historic large fire occurrence for the states of Washington and Oregon, to evaluate the potential use of the Growing Season Index (Jolly et al. 2005) to identify the start and end of fire season. Results are presented using the Northwest Coordination Center's predictive service areas as the spatial unit of analysis.