A bank burns on Sunset Boulevard. Image take on January 8 by Cal Fire.
Starting on January 7 2025 two large wildfires (the Palisades and Eaton wildfires) erupted in Los Angeles, California. The fires spread extremely quickly over the following week and are among the most destructive of human property in Southern California’s history.
At the time of writing, the fires are not fully contained and other fires have emerged in the San Diego area (CNN, 2025), and the full extent of the destruction will only become apparent over the coming weeks and months. To date at least 28 people are known to have lost their lives and more than 16,000 structures have been destroyed (CAL FIRE).
Coastal Southern California has a Mediterranean climate with fire-adapted chaparral shrubland, grasses, and oak trees. Wildfire is a natural part of the local ecosystem, with some species even depending on it. Wildfires are typically largest from July to September due to low fuel moisture caused by lack of precipitation in summer, high temperatures, and low humidity. However, some of the region’s most destructive events occur in fall or early winter due to the arrival of the Santa Ana windy season.
This particular event stands out due to the speed of fire spread and the challenge of suppressing it due to exceptionally strong Santa Ana winds. These dry winds occur in Coastal Southern California when air flows toward the coast from inland mountains. These winds typically happen in the cooler months from October-March, as cooling over the Great Basin leads to the formation of a high-pressure system (Abatzoglou et al., 2013). This type of synoptic circulation pattern was observed at the start of the fires and the 7th and 8th January 2025, and was strengthened by a mid-troposphere “cut-off-low” weather system that came off the higher-latitude jet stream and traveled to Baja California.
The typical seasonal arrival of rainfall from October-December typically marks the end of the wildfire season, nullifying the ability of Santa Ana winds to easily spread large and intense fires. However, the region has not experienced significant rainfall since May 2024, meaning grasses and brush were dry and highly flammable when the fires broke out. Additionally, above-average precipitation in winters of 2022/23 and 2023/24 had previously encouraged vegetation growth, providing more fuel for the fires.
Human-induced climate change is increasing wildfires in many regions of the world, as hot, dry and windy weather conditions increase the risk of fires both starting and spreading. Researchers from the United States, the Netherlands, Denmark, Belgium, France, Sweden and the United Kingdom collaborated to assess to what extent human-induced climate change altered the likelihood and intensity of the weather conditions that fuelled the LA wildfires, and how the conditions will be affected with further warming.
Fig. 1: Map of FWI based on ERA5 data on 8th of January 2025, showing very high indices around LA (black cross). The black polygon denotes the study area and corresponds to Coastal Southern California. » …