Do fire danger classes in Croatia need calibration?

The Canadian Fire Weather Index (FWI) System was calibrated for Croatian Adriatic some 40 years ago. Five fire danger classes were introduced, which since then have been in use for fire danger assessment during the fire season. In the presence of climate change the fire danger is continuously growing, leading to the need for a review of the Fire Weather Index System and eventually a new calibration. In this paper, a simple analysis of the highest danger class was performed to determine whether there are reasons for revision of fire danger classes and possible introduction of the extreme danger class. The results show rather high occurrence of the very high danger class, 20% of cases in the fire season and 25% during the peak of fire season (July and August). The percentile values of FWI and BUI obtained by the large fire (burned area > 400 ha) analysis, especially the 50
^th
percentile, with a 3% occurrence rate in average, can be used as an indicator of the specific fire weather conditions that can be described with an extreme fire danger class.