Los Angeles Wildfires of January 2025: A Convergence of Climate and Human Factors
Highlights
- Back-to-back wet winters, a record-dry fall, and strong Santa Ana winds fueled the January 2025 fires.
- Low fall precipitation had a significant impact on vegetation moisture.
- Global warming and La Niña conditions equally contributed to extreme fire weather.
- Effective strategies to reduce risk include controlling human ignitions, using fire-resistant materials, and strategic development.
On January 7, 2025, wildfires erupted in the Los Angeles metro area, devastating multiple neighborhoods. The blazes killed over two dozen people, destroyed more than 15,000 homes and businesses, and caused widespread air quality issues. The Eaton Fire and Palisades Fire, two of the largest, now rank second and third on California’s list of most destructive fires.
The Pacific Palisades Fire near Malibu, California, which started on January 7, 2025. Adobe stock photo.
The fires were a result of a dangerous combination of human and natural factors. While the ignitions were human-caused, the severity was exacerbated by high population density and building patterns that placed homes near chaparral landscapes. The region experienced record amounts of flammable vegetation due to wet winters followed by extreme heat and dryness, culminating in powerful Santa Ana winds.
Tim Brown, Director of NOAA’s Western Regional Climate Center, noted that fires in Southern California are a result of the intersection of climate, people, topography, and fuels. He emphasized that while human-caused climate change is a factor, it is not the sole cause.
The Weather and Seasonal Climate Context of the Los Angeles Fires
Southern California has a Mediterranean climate with hot, dry summers and mild, wet winters. The fire season typically peaks in early fall when vegetation is dry, but Santa Ana winds are starting to blow. The 2022-23 and 2023-24 wet seasons were unusually wet, leading to lush vegetation. However, summer and fall 2024 saw near-record high temperatures, drying out the landscape. As La Niña developed, the region experienced exceptionally dry conditions from October to December.
October–December 2024 was exceptionally dry across the U.S. Southwest. The balance between precipitation and evaporation (the Standardized Precipitation Evaporation Index) was strongly negative (brown colors) around Los Angeles. NOAA Climate.gov map, based on PRISM data.
By the end of 2024, the area around Los Angeles was experiencing its driest start to the wet season on record, with no measurable precipitation. Vegetation was parched, and experts warned of record-high flammable vegetation. A final extreme: a Santa Ana wind event forecasted to produce near-record wind speeds, set the stage for the devastating fires.
On the morning of January 8, 2025, forecasts were calling for a rare wind event for the mountains surrounding Los Angeles. These maps show forecasts for wind gusts at 13Z (5 a.m. local time) for different thresholds. Wind gusts above the 75th percentile were forecasted for a large area (top left). A more limited, but still significant area was forecasted to have winds above the 90th percentile (top right). Directly over the location of the Palisades and Eaton Fires, winds were forecasted to gust above the 98th percentile (bottom left), and in the surrounding mountains, some gusts were forecast to exceed the historic maximum (bottom right). NOAA Climate.gov graphic, adapted from original by Dan McEvoy.
Climate Change and Fires in California and the Southwest
Experts have concluded that fires in California and the Southwest have become larger and more severe due to human-caused warming. This warming increases evaporation, making dry spells even drier and extending the fire season. Human-caused warming trends may be responsible for nearly two-thirds of the observed increase in summer fire weather conditions over the past 40 years.
However, fall and winter fires in Southern California, such as the Eaton and Palisades Fires, may be less sensitive to high temperatures and more to low precipitation. A preliminary analysis by UCLA researchers found that the fuel moisture content of small-diameter woody vegetation was extremely low just before the fires broke out, indicating extremely flammable conditions.
Observed fuel moisture in the area around Los Angeles from January 1, 2024, through Jan 7, 2025. Fuel moisture was above average in the first half of 2024, but dropped well below average in fall 2025. Additional lines show that fuel moisture would have been only slightly below average if temperature, humidity, and precipitation had been near normal after June 1 (blue line). The turquoise line shows estimated fuel moisture if the observed high temperatures and low humidity had been accompanied by normal precipitation. The brown line shows estimated fuel moisture if the observed low precipitation had been accompanied by normal temperature and humidity. NOAA Climate.gov graph, adapted from original by Gavin Madakumbura.
La Niña and Climate Change Influence on Record-Dry Fall
The developing La Niña likely had an independent, similarly sized influence on the extreme fire weather conditions. The combination of global warming and La Niña made such conditions about 75 percent more likely than in a cooler, pre-industrial climate. Statistical and Earth system models showed that dry spells as extreme as the October-December 2024 period are 2.4 times more likely in today’s warmer climate than they would have been without human-produced greenhouse gases. La Niña made the extreme dryness 1.8 times more likely than in an ENSO-neutral state.
While some portion of the observed drying trend may be due to natural climate variability, the qualitative result—that the drought season is getting longer, rains are decreasing, and this is due to human-induced climate change—has been assessed thoroughly in the last IPCC report.
Record Wet to Record Dry: Bad Timing, or Part of a “Climate Whiplash” Trend?
The transition from record-wet to record-dry conditions may be influenced by greenhouse-gas driven warming. Southern California’s climate is characterized by seasonal extremes, with hot, dry summers and wet winters. However, the wet seasons are also variable, with La Niña typically coinciding with the skimpiest wet seasons and El Niño with the most abundant.
This variability gives rise to what Daniel Swain describes as hydroclimate whiplash, a sudden shift between a location’s wettest and driest conditions. Swain and John Abatzoglou suspect that rising global temperatures are intensifying both wet and dry extremes. Warmer atmospheres can hold more water vapor, leading to more precipitation during wet events, and are thirstier for moisture during dry periods, intensifying drought.
The decline in fall precipitation over the past six decades has delayed the start of the wet season by almost a month. Combined with warming, this trend is stretching the fire season into the winter months, coinciding with the peak of the Santa Ana wind season.
Preliminary analysis from the World Weather Attribution team found that in a cooler, pre-industrial climate (top bar), the most extreme periods of drought (red) occurred in early fall, and rarely overlapped the Santa Ana wind season (middle bar). In today’s warmer climate (bottom bar), highly flammable conditions persist later in the year, increasing the chance a wildfire will break out during the peak of the Santa Ana winds in December and January. Graphic by World Weather Attribution team.
The past few years in California exemplify hydroclimate whiplash, a pattern projected to increase due to greenhouse-gas-driven warming. While there is no clear trend yet in the “wettest wets,” there is a clear trend toward “drier dries,” leading to statistically significant increases in extreme fire weather conditions between November and January.
Swain and Abatzoglou estimated that warming and drying have increased average fire weather conditions over November-January by 36 percent. This extension of the dry season at the worst possible time due to Santa Ana winds significantly increases fire risk.
Preparing for Fire in a Warming Climate
The most effective near-term strategies to lower fire risk in Southern California involve local actions: aggressive suppression of human ignitions during extreme fire weather, hardening homes and structures with fire-resistant materials and landscaping buffers, and locating urban development in lower-risk areas.
A receding line of brick chimneys from homes burned by the Eaton Fire. Photo by Steve Lyon, via Flickr. Cropped from the original. Used under a Creative Commons license.
Understanding the influence of climate change on extreme events like the Los Angeles fires is crucial for community infrastructure and planning, local and state economic well-being, and insurance markets. However, at the individual level, the most important question is whether you are ready now.
As we face an increasingly volatile climate, preparing for extreme events is essential. Whether it’s fires in California, tornadoes in the South, or flooding in the Northeast, being ready can make a significant difference.
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