Megafires in Mediterranean Europe: the compound role of fire weather and drought

This study investigates why some wildfires in Mediterranean Europe escalate into very large fires or megafires, while others remain smaller. Using data from 11,403 summer wildfires between 2008 and 2022, the authors analyse how short-term fire weather conditions and longer-term drought and fuel stress interact to drive fire-size transitions. The research combines official fire perimeter data with high-resolution environmental and drought datasets and applies machine learning and logistic regression models to identify the factors most strongly associated with the growth of fires into large, very large, and mega events.

The study finds that very large fires are most likely when anomalously hot, dry, and windy conditions occur on already stressed fuels under multi-month drought. The transition to megafires, however, is especially associated with exceptionally warm nights and strong winds near ignition, rather than stronger vegetation anomalies alone. The models show that these transitions can be predicted with reasonable accuracy, with up to two-thirds of megafires correctly identified out of sample. Overall, the findings highlight that megafires in Mediterranean Europe emerge from the combination of drought-preconditioned fuels and extreme short-term fire weather, emphasizing the need to manage fuel continuity and prepare for persistent hot, dry, and windy conditions in a warming climate.