Southern California Wildfires: A Retrospective Analysis

Introduction

The Southern California wildfires continue to burn across Los Angeles County, with newly revealed satellite imagery providing insight into the recent weather events that fueled the blazes.

Weather Conditions and Vegetation

According to data from NASA Landsats, warm and dry weather in Los Angeles in the last two-thirds of 2024 primed the vegetation to catch fire, and for that fire to spread quickly. The largest fires started on January 7 and devastated swathes of L.A., including Pacific Palisades and Altadena.

Strong Winds and Fire Spread

The fires spread quickly due to dry conditions and strong winds from the east that blew the fires across the city and kickstarted new blazes. According to Cal Fire, the two largest fires—the Palisades and Eaton fires—are 98% and 99% contained, respectively.

Satellite Imagery and Retrospective Analysis

A team of researchers at the University of California, Los Angeles, found that a buildup of vegetation between 2022 and 2024, followed by the aforementioned dry conditions, made Los Angeles county a giant tinderbox. Satellite imagery offers a retrospective look at how the seeds of the fires were sown by recent climatological trends.

Atmospheric Rivers and Vegetation

2022 and 2023 were especially wet years for Southern California; according to a NASA Earth Observatory release, rainfall totals for downtown L.A. were nearly twice the average both years. Atmospheric rivers are regular occurrences on the west coast, especially the Pacific Northwest. These rivers dump rainfall over an area over an extended period of time, often causing flooding and landslides.

Soil Moisture and Vegetation

But the wetness also quenched the thirst of plants, as shown in the map above. Vegetation built up across L.A. County—up to 30% more than average in some parts of town—in summer 2024. The National Interagency Fire Center stated in July that an above-average amount of vegetation was available as fuel for California wildfires to burn.

Drought Conditions and Fire Risk

During the second half of 2024, conditions rapidly changed. The region dried up, in turn parching all the vegetation that had proliferated during the years of intense rainfall. According to the Los Angeles Times, the period from May 2024 through January 2025 was the second-driest on record dating back to 1877.

Conclusion

In the map above, the dryness of the soil is laid bare. The map shows soil moisture levels relative to normal in the top 40 inches of soil—where most plants lay their roots. The maps are a reminder that even though the fires felt sudden and surprising, the conditions on the ground were primed for disaster. As climatological swings from very wet to very dry become more common, it’s crucial that we have satellites surveying areas and—hopefully—giving as much warning as possible if a disaster is around the corner.