Assessing fire danger classes and extreme thresholds of the Canadian Fire Weather Index across global environmental zones: a review

Fire weather indices are one of the basic components of any fire danger early warning system. The Canadian Fire Weather Index (FWI) was developed to indicate the danger due to wildfires in boreal and temperate forests in Canada in the second half of the 20th century. Over time, the FWI has been adapted all over the world and is considered the most widely used fire weather index. This study provides a comprehensive review and meta-analysis of 750 research papers, generalizing the adoption of the FWI across 18 global environmental zones. The objective was to determine FWI values for various fire danger classes worldwide, from very low to extreme. The values of FWI and hydrometeorological variables were compared with wildfire occurrence. Key findings indicate that in drier and warmer climates, higher FWI values (around 50) correspond to high fire danger, whereas in cooler and moister climates, lower FWI values (around 25) signify extreme danger. The analysis of hydrometeorological variables reveals that relative humidity, aridity index, and vapor pressure deficit are significant factors influencing extreme minimum FWI, while average solar radiation has minimal impact. These insights have critical implications for developing effective wildfire prevention and management strategies tailored to specific environmental conditions. By establishing new fire danger classes reflective of regional meteorological and hydroclimatic characteristics, this study enhances the global applicability of the FWI. The ability to quickly adapt the FWI for fire danger forecasting in new areas is particularly beneficial for regions with previously low study coverage. The results underscore the importance of integrating regional climate variables into fire danger assessment frameworks to improve early warning systems and mitigate wildfire risks. The conclusions highlights the effectiveness of the FWI in diverse geographic contexts and its potential to enhance fire danger forecasting globally, thereby aiding in the prevention and management of wildfires.