Record-breaking wildfire intensity and nocturnal spread during the extreme 2025 wildfire season in Southwestern Europe: causes and impacts

Abstract

Europe faced an extreme wildfire season in 2025, with nearly 700,000 ha burned in the Iberian Peninsula (IP) alone. Here, we analyze the drivers and impacts of the 2025 wildfire season in the IP and its significance within the ongoing global pyrocrisis. Decades-long declines in burned area, driven by increased fire suppression, appear to be changing after an inflection point in 2022. Fire intensity has escalated over the last two decades, and estimated fire radiative energy in 2025 approached the annual output of a 1,000 MW nuclear reactor. Despite an unusually wet spring, an extreme summer heatwave triggered a flash drought, dehydrating fuels below critical thresholds. Remarkably, 29-42% of all analyzed wildfires spread faster at night than during the day, a seldom-reported phenomenon likely due to interactions between surface weather, atmospheric instability and, potentially, pyroconvection. Increases in fire intensity likely facilitated the overwhelming of suppression efforts during simultaneous fire events that may have been manageable decades ago. Wildfires expanded into previously fire-free high-altitude regions, and fire-size distributions changed markedly, including the largest wildfire in record and the highest proportion of burned area by fires exceeding 5,000ha. Impacts included 1595–2291 estimated premature deaths from smoke exposure and significant effects on protected areas. Initial rates of fire spread varied substantially across fuel models, indicating the importance of land management. These results reveal shifts in key components of fire regimes, including unprecedented nocturnal fire acceleration and fire intensity, with escalating impacts on human health and ecosystems where fuel management remains the main option to curb increasing fire intensity.