What Started the Fires in Los Angeles?

How many fires are burning in Los Angeles County and where are they?

Six major fires started during the Santa Ana wind event last week:

• The Palisades Fire, in the Pacific Palisades, which has burned nearly 24,000 acres, started on Tuesday, January 7, around 10:30 a.m. Pacific time.
• The Eaton Fire, north of Pasadena, which has burned more than 14,000 acres, started on Tuesday just after 6:00 p.m.
• The Hurst Fire, in the northern edge of the San Fernando Valley, which has burned about 800 acres, started on Tuesday night around 10:30 pm.
• The Lidia Fire, in Acton, California, just north of Angeles National Forest, which has burned roughly 400 acres, started on Wednesday afternoon around 1:00 p.m. As of Saturday morning it was declared 100% contained.
• The Sunset Fire, in the Hollywood Hills, which has burned about 43 acres, started on Wednesday night around 5:30 p.m. Evacuation orders lifted early Thursday morning, when the fire’s “forward progress has been stopped,” and crews were working to “put out hotspots within the fire perimeter and keep the wind from spreading embers,” according to Los Angeles Fire Department Public Information Officer Erik Scott.
• The Kenneth Fire, in the hills above Calabasas, which burned a little over 1,000 acres, started on Thursday around 3:30 p.m. As of Sunday morning it was declared 100% contained.

How did the fires start?

Officials are investigating the cause of the fires and have not made any public statements yet. Early eyewitness accounts suggest that the Eaton Fire may have started at the base of a transmission tower owned by Southern California Edison. So far, the company has maintained that an analysis of its equipment showed “no interruptions or electrical or operational anomalies until more than one hour after the reported start time of the fire.” A Washington Post investigation found that the Palisades Fire could have risen from the remnants of a fire that burned on New Year’s Eve and reignited.

On Thursday morning, Edward Nordskog, a retired fire investigator from the Los Angeles Sheriff’s Department, told me it was unlikely they had even begun looking into the root of the biggest and most destructive of the fires in the Pacific Palisades. “They don't start an investigation until it's safe to go into the area where the fire started, and it just hasn't been safe until probably today,” he said.

It can take years to determine the cause of a fire. Investigators did not pinpoint the cause of the Thomas Fire until March 2019, more than two years after it started.

But Nordskog doesn’t think it will take very long this time. It’s easier to narrow down the possibilities for an urban fire because there are typically both witnesses and surveillance footage, he told me. He said the most common causes of wildfires in Los Angeles are power lines and those started by unhoused people. They can also be caused by sparks from vehicles or equipment.

How do these fires compare to past fires in California?

At more than 40,000 acres burned total, these fires are unlikely to make the charts for the largest in California history. But because they are burning in urban, densely populated, and expensive areas, they could be some of the most devastating. With an estimated 9,000 structures damaged as of Friday morning, the Eaton and Palisades fires are likely to make the list for most destructive wildfire events in the state.

And they will certainly be at the top for costliest. The Palisades Fire has already been declared a likely contender for the most expensive wildfire in U.S. history. It has destroyed more than 5,000 structures in some of the most expensive zip codes in the country. Between that and the Eaton Fire, Accuweather estimates the damages could reach $57 billion.

Why are these fires so bad? Is it climate change?

While we don’t know the root causes of the ignitions, several factors came together to create perfect fire conditions in Southern California this week.

First, there’s the Santa Ana winds, an annual phenomenon in Southern California, when very dry, high-pressure air gets trapped in the Great Basin and begins escaping westward through mountain passes to lower-pressure areas along the coast. Most of the time, the wind in Los Angeles blows eastward from the ocean, but during a Santa Ana event, it changes direction, picking up speed as it rushes toward the sea.

Jon Keeley, a research scientist with the US Geological Survey and an adjunct professor at the University of California, Los Angeles told me that Santa Ana winds typically blow at maybe 30 to 40 miles per hour, while the winds this week hit upwards of 60 to 70 miles per hour. “More severe than is normal, but not unique,” he said. “We had similar severe winds in 2017 with the Thomas Fire.”

Second, Southern California is currently in the midst of extreme drought. Winter is typically a rainier season, but Los Angeles has seen less than half an inch of rain since July. That means that all the shrubland vegetation in the area is bone-dry. Again, Keeley said, this was not usual, but not unique. Some years are drier than others.

These fires were also not a question of fuel management, Keeley told me. “The fuels are not really the issue in these big fires. It's the extreme winds,” he said. “You can do prescription burning in chaparral and have essentially no impact on Santa Ana wind-driven fires.” As far as he can tell, based on information from CalFire, the Eaton Fire started on an urban street.

While it’s likely that climate change played a role in amplifying the drought, it’s hard to say how big a factor it was. Patrick Brown, a climate scientist at the Breakthrough Institute and adjunct professor at Johns Hopkins University, published a long post on X outlining the factors contributing to the fires, including a chart of historic rainfall during the winter in Los Angeles that shows oscillations between wet and dry years over the past eight decades.

But climate change is expected to make dry years drier and wet years wetter, creating a “hydroclimate whiplash,” as Daniel Swain, a pre-eminent expert on climate change and weather in California puts it. In a thread on Bluesky, Swain wrote that “in 2024, Southern California experienced an exceptional episode of wet-to-dry hydroclimate whiplash.” Last year’s rainy winter fostered abundant plant growth, and the proceeding dryness primed the vegetation for fire.