How big are the California wildfires – and why have they spread so quickly?

At least 10 people have been killed and some 10,000 homes and other buildings have been burned in wildfires that have ravaged multiple parts of Los Angeles in California – the most populous state of the United States.

Nearly 180,000 residents in different neighbourhoods of Los Angeles city have been ordered to evacuate as the fires, which erupted on Tuesday, continue to rapidly spread, fuelled by high winds.

So how big are the fires at present, and how did they begin?

What started the California wildfires?

The first fire started in the Pacific Palisades neighbourhood of Los Angeles at 10:30am (18:30 GMT) on Tuesday, according to California Department of Forestry and Fire Protection (Cal Fire).

Investigators are still trying to find out the exact trigger for the worst firestorm in recent memory, but a combination of factors might have created conditions optimal for a fire.

California generally experiences wildfires during June and July, and they can run until October, but the blaze has defied the calendar this year, erupting in January – the coldest of the winter months.

Southern California, the site of the fires, has been experiencing drought conditions and has not seen significant rainfall for months. The US Drought Monitor’s latest map shows that as of December 31, 2024, 40.9 percent of the California is drought free. Last year around this time, as of January 2, 2024, 96.65 percent of California was drought free.

Climate change has contributed to an increase in the frequency, season length and burned area of wildfires, according to a report by the US Environmental Protection Agency (EPA).

So, dry conditions aided by Santa Ana winds – dry and hot winds common in the area – most likely caused the wildfires.

The dry desert air moves from the interior of the region towards the coast and offshore. It contributes to wildfires because it significantly reduces humidity in the environment due to its dry nature. This causes vegetation to become very dehydrated and susceptible to fire. Under these circumstances, any spark can start a fire, be it from a cigarette butt, vehicle or power line.

Gusts up to 100mph (160km/h) were recorded at higher elevations on Tuesday night, according to AccuWeather meteorologist Danielle Ehresman.

Besides dry vegetation, Los Angeles has other flammable materials such as low-hanging power cables and wooden telephone polls.

Santa Ana winds have been associated with extreme wildfires in California in the past, including the Woolsey fire in November 2018, which killed three people and razed 1,600 structures.

Experts, however, warn that weather conditions are dire this year.

“We really haven’t seen a season as dry as this one following a season as wet as the previous one – all of that extra abundant growth of grass and vegetation followed immediately by a wind event of this magnitude while it’s still so incredibly dry,” Daniel Swain, a climate scientist at University of California, Los Angeles, said on a livestream on Monday.

How big are the California wildfires?

Rapid spread

The fire started in Palisades located on the Pacific Ocean, and from there the blaze spread rapidly to other neighbourhoods. The second fire broke out in Eaton at about 6pm (02:00 GMT) on Tuesday. A third fire, called the Hurst fire, also broke out the same day in Sylmar, in the San Fernando Valley northwest of Los Angeles.

Five more fires broke out in California on Wednesday: the Lidia, Sunset and Woodley fires in Los Angeles; the Olivas fire in Ventura and the Tyler fire in Riverside. On Friday it was reported that a new fire – the Kenneth fire – had also broken out in West Hills, a neighbourhood in the San Fernando Valley.

“The extraordinary winds are the main driver – literally,” said Stephen Pyne, emeritus professor at Arizona State University’s School of Life Sciences. “These are near-hurricane force winds. There is no firepower on Earth capable of stopping the flames; they quickly blow past any initial responses fire crews can make, and they will continue until the winds cease or they run out of fuel [eg, the Pacific Ocean].

“A primary mechanism for fire spread is not a tsunami of flame: it’s a blizzard of embers. The embers can kindle buildings well ahead of the flaming front. The structures then become a primary fuel, and the fire spreads as an urban conflagration, leaping from structure to structure.”

Amount of land burned

According to Cal Fire, here is the current status of the major fires as of Thursday night:

• Palisades: At least 19,978 hectares (49,367 acres)
• Eaton: At least 13,690 hectares (33,829 acres)
• Hurst: At least 771 hectares (1,905 acres)
• Lidia: At least 348 hectares (860 acres)
• Kenneth: At least 960 hectares (2,372 acres)

Here is a comparison of aerial images of the Pacific Coast Highway before and after the Palisades fire.

And here is Altadena before and after the Eaton fire.

Containment

The containment percentage of a fire refers to the perimeter or containment line established around the fire by firefighters to prevent it from spreading further. A containment line can be any physical barrier around the fire, such as a shallow trench dug into dirt.

The fires in California are barely contained, which means there is no prevention from them spreading further. The Palisades, Eaton and Sunset fires are all zero percent contained, while the Hurst fire is 10 percent contained and the Lidia fire is 40 percent contained.

The Woodley, Olivas and Tyler fires are 100 percent contained, according to Cal Fire.

What has the government’s response been?

The scale of the fires has got out of hand, according to the local firefighting department.

California Governor Gavin Newsom said in an X post on Wednesday night that 7,500 firefighting personnel are currently on the ground.

US President Joe Biden cancelled an upcoming Italy trip to focus on the federal response to the fire, the White House said.

Biden posted on his X account that his team has provided 5 air tankers and 10 firefighting helicopters. However, the strong winds have hindered aerial rescue efforts.

Los Angeles County Fire Chief Anthony Marrone told a news conference that firefighters from six other states including Nevada were being rushed to California. Additionally, 250 engine companies with 1,000 personnel were being moved from Northern California to Southern California.

But resources are running thin.

Water shortages in the Palisades have dried out some fire hydrants.

Janisse Quinones, the chief executive of the Los Angeles Department of Water and Power, told a media conference that Pacific Palisades depends on three tanks containing about a million gallons (3.78 million litres) each. Quinones added that the demand for water to extinguish fires at lower elevations was creating difficulty in refilling water tanks at higher elevations.

The Los Angeles Fire Department (LAFD) has issued evacuation orders for Hollywood, Hurst and the Palisades. Click here to view LAFD’s interactive evacuation map.

“The fires are not over and they won’t end until the winds die down – not just the Santa Ana winds over and down the mountains, but the local winds that will move into the Santa Anas retreat,” said Pyne. “When [and if] winter rains finally arrive, they could lead to hillside erosion and debris flows.”

What’s next?

Winds have weakened to about 30-50mph (50-80km/h), but fires are still active.

Unfortunately, winds are expected to pick up speed on Friday morning. However, these will not be as intense as the winds that intensified the fires on Tuesday and Wednesday.

The winds are predicted to subside later on Friday, and red flag fire warnings will be removed by later that evening.

However, the fires will remain difficult to contain, experts say.

“Post-fire cleanup will be messy, long and expensive,” said Pyne.

“Contemporary houses are filled with plastics, synthetics and electronics that can be toxic. Rebuilding will be a nightmare – it’s hard to see how insurance can pay; even state-supported supplements will fall short.”