Hot Drought Increased the Occurrence Probability of the 2025 Los Angeles Destructive Wildfires

The western Los Angeles (LA) wildfires of early January 2025 caused catastrophic social and environmental impacts, drawing widespread attention. This study investigates the characteristics of these wildfires and quantifies the influence of heat and drought on their likelihood using a copula-based Bayesian probability framework. The wildfires were characterized by burned area (BA) and intensity (fire radiative power, FRP). The criteria establishing the presence of “hot drought” conditions were identified using the 5-day Standardized Temperature Index (STI) and 75-day Standardized Precipitation Index (SPI), respectively. The wildfire outbreak began on 7 January 2025 and burned for more than six days, with the total burned area exceeding 245 km² and the cumulative FRP exceeding 41,060 MW. Based on satellite-derived active fire observations from 2001 to 2025, we estimate that such large and intense wildfires during LA’s rainy season represent a once-in-a-67-year event. The wildfires were largely driven by the combination of hot and dry conditions, which dried out soils and vegetation that had proliferated due to above-average precipitation in previous winter seasons, thereby providing abundant fuel. Our seasonal analysis reveals that extreme drought increased the probability of wildfires matching the 2025 intensity and BA by 54% and 75%, respectively. Hot drought further amplified these probabilities by 149% (intensity) and 210% (BA). These findings suggest an elevated risk of large wildfires under hot drought conditions, contributing to their expansion into the non-traditional fire season.