In early January 2025, several wildfires erupted near Los Angeles, California. As Santa Ana winds exceeding 100 mph tore through the canyons, the fires rapidly spread. The fires killed 29 people and destroyed thousands of structures, causing billions of dollars of damage. While hurricane-force winds played a role, they were not the only climate-related factor. Two years of exceptional rainfall from 2022 to 2024 were followed by a summer of extreme drought. This so-called hydroclimate whiplash fostered the widespread growth of vegetation that then dried out and fed the Palisades and Eaton fires.
This pair of maps from NASA Earth Observatory tells the story. They used data from NASA satellites to show how vegetation health and soil moisture created potential fuels for the fires.
The first map focuses on how vegetation in summer 2024 compared to averages from 1991 to 2020. The Normalized Difference Vegetation Index (NDVI) is a measure of vegetation health and abundance. Darker greens indicate areas with more dense and healthy vegetation than normal. In both Pacific Palisades and Altadena (where the Palisades and Eaton fires occurred), the map shows lots of healthy vegetation in summer 2024.
The second map highlights soil moisture on January 7, 2025, the day the fires ignited. In this map, dark browns show exceptionally low soil moisture. On the day the fires started, soil moisture was extremely low in the Pacific Palisades and Altadena areas. The healthy, abundant vegetation from summer 2024 had dried out. When combined with high winds, it created the conditions where the wildfires could thrive.
These maps help explain how the fires became so destructive. But they also offer a warning. The most alarming takeaway from the second map is the range of dry soils. They span coastal areas from San Diego in the south to Point Conception in the north. While recent rains have brought much-needed moisture, this map reveals a potentially dangerous situation in Southern California.
More to Explore
- Take a global look at fire potential in wildland-urban interface areas.
- Revisit drought conditions across the US since 2000.
