Wildfire · Southern California, United States
Los Angeles: fire in January
On 7 January 2025 a dry wind from the desert, gusting near hurricane force in the mountains, swept down through the hills around Los Angeles. Fires broke out in Pacific Palisades and above Altadena and ran into the city faster than anyone could stop them. Within days more than 16,000 homes and buildings had burned and at least 28 people had died. It was the middle of what should have been the rainy season.
7–31 January 2025 · Los Angeles, California · CAMS, ERA5
7mm
ERA5 rain, October–December 2024
At the Palisades grid point, in what is normally the start of the rainy season.
1,127µg m⁻³
Surface PM2.5, 9 January
CAMS daily mean near the Palisades; the January normal there is 34.
35%
More likely in today's climate
Hot, dry, windy conditions like those of early January 2025, against the pre-industrial climate.S1
What happened
The Palisades fire started on the morning of 7 January in the Santa Monica Mountains above Pacific Palisades; that evening the Eaton fire broke out in the San Gabriel foothills above Altadena. Driven by the wind, both ran downhill into neighbourhoods, and the gusts grounded the aircraft that might have slowed them. Embers carried far ahead set houses alight blocks away from the fire front.
The fires burned for weeks. Together they destroyed more than 16,000 structures and killed at least 28 people, the most destructive fire disaster in Los Angeles's history.S1
The Santa Ana
Santa Ana winds blow when high pressure builds over the Great Basin, inland, and the air flows down towards the coast. Descending, it is compressed and warms, and its humidity drops to a few percent. Funnelled through the passes and canyons, it reaches the coast as a hot, dry, gusty wind from the north-east, the opposite of the usual sea breeze.
On the night of 7 to 8 January the Lab's maps show the offshore wind across the Los Angeles basin and dew points near −10 °C over the Palisades: air as dry as a desert's.
A winter without rain
The two winters before had been wet, February 2024 especially, and grass and brush had grown thick on the hills. Then the rain stopped. From May 2024 to the fires, Los Angeles had almost none: in ERA5, October to December 2024 brought 7 mm at the Palisades, where a year earlier the same months brought 88 mm. The new growth dried into fuel.
An attribution study found that the hot, dry, windy conditions of early January 2025 were about 35 % more likely than in the pre-industrial climate, and that warming has lengthened the dry season into the months when Santa Ana winds blow.S1
| Month | 2024–25 | 2023–24 |
|---|---|---|
| October | 1 | 2 |
| November | 4 | 17 |
| December | 1 | 70 |
| January | 15 | 55 |
| February | 75 | 242 |
Smoke over the city
×33
CAMS daily PM2.5 near the Palisades on 9 January against the January normal. The smoke, carried out to sea by the offshore wind, returned over the coast when it weakened.
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References
News
Studies and guidelines
- S1World Weather Attribution (2025). Climate change increased the likelihood of wildfire disaster in highly exposed Los Angeles area. January 2025.The attribution of the fire weather to climate change, the dry season's overlap with the Santa Ana, and the toll.