Why did the Los Angeles fires spread so quickly? Here are 5 reasons

The fire spread with terrifying speed as residents of the Pacific Palisades neighborhood west of Los Angeles watched smoke rise from the hills across from their homes on the morning of Jan. 7, as the blaze reached about 10 acres. In just 25 minutes, the blaze had grown to more than 200 acres.

Over the next few hours, the flames spread to homes, theaters, restaurants, stores and schools. By the morning of Jan. 9, the Palisades Fire had burned 17,234 acres, and other fires were burning across the Los Angeles area, making it one of the worst fires in the city’s history, according to AccuWeather’s chief meteorologist, Jonathan Porter.

So why were the fires so intense, and why did they spread so quickly? Here are five reasons:

Rapid increase in flammable materials

“Rain is often thought of as a bad thing for fires,” says Rory Hadden, a fire scientist at the University of Edinburgh. “If it rains during a fire, it’s bad.” But pre-fire rainfall can lead to dense vegetation growth, which can provide potential fuel.

"When a dry season comes, these plants dry out very quickly, and they are in greater quantities, which leads to the accumulation of more flammable materials," he added.

Fire scientist Maria Lucia Ferreira Barbosa, from the UK's Centre for Ecology and Hydrology, said in a statement that a period of wet weather in 2024, followed by a dry period, created "ideal conditions for the spread of wildfires."

This transition from very wet to very dry weather is called “hydroclimate variability.” A recent study showed that the risk of these hydroclimatic variability has increased globally by between 31 percent and 66 percent since the mid-20th century.

santa ana winds

The fires were also fanned by a strong windstorm that pushed the flames, which started in the foothills west of Los Angeles, further spread through dry vegetation and engulfed the Pacific Palisades neighborhood near Santa Monica.

The wind itself is often hot and dry, so it can take moisture away from plants and make them even drier.

“In every wildfire, there are three things: an ignition source, a flammable object, and some oxygen from the air,” Haden says. “But the thing that made these fires so big was the wind speed coming out of the middle of the California desert.”

These winds are known as Santa Ana winds, or Fawn winds, and can cause wildfires to break out irregularly.

“These winds are very dry, and they move very quickly, so once a fire starts, it's very easy for the fire to grow and spread very quickly,” Haden said. “We've seen winds in excess of 100 miles per hour.”

"These high wind speeds will fan the flames and push those fires from wherever they started very quickly across the landscape," he adds.

In some cases, these windstorms can start fires themselves, causing power cables to fall and ignite nearby plants.

fire shards

Not only does this terrain increase the risk of fires spreading, it also makes evacuations more difficult. In the Palisades area, narrow roads on the hills pose an additional challenge for people trying to leave, Mike Bonin, a former Los Angeles City Councilman, told The New York Times.

climate change

Although it is too early to say whether or how much climate change is playing a role in these fires, wildfires around the world have been linked to climate change. The number of days when the weather affects the likelihood of fires is increasing, and climate change is making these conditions more severe, Matt McGrath reports for BBC News.

The danger is not simply a result of global warming, says Haden, but rather the diversity of phenomena we are seeing. “It’s not just the hot weather, it’s the combination of stronger winds and rain that allows plants to grow,” he says.

“We are facing massive changes in not only hotter and drier weather, but also wetter, windier weather, and all the other climate-related factors, and these factors are what will determine the level of risk in the future,” he continues.

Source: BBC