The relationship between fire activity and fire weather indices at different stages of the growing season in Finland

This study examines the relationship between predicted fire hazard and observed fire activity at different stages of seasonal vegetation development. The data consisted of Finnish national fire records 1996-2003, the daily values of the effective temperature sum of over 5 °C, the Finnish Fire Risk Index, and the FWI and ISI codes of the Canadian Fire Weather Index System. The highest probabilities for fire-day and multiple-fire-day occurrence were found during the final stage of the growing season, at the temperature sum value of above 900. The probability of large-fire-day was highest during the early stages of the growing season. The statistical significance of the probability models was poorest during the initial and final stages of the season.