On Jan. 20, nearly two weeks after the Eaton fire broke out, investigators were examining transmission towers, which had visible signs of smoke residue that appeared to have resulted in a brown discoloration on the structure — features that distinguished them from other towers in the area.

Firefighters have begun to slow the spread of the Border 2 fire, which started Thursday in the mountains near the U.S.-Mexico border and has scorched 6,625 acres of wilderness in San Diego County. Some 7,000 people have evacuated from areas near the fire, which is 10 percent contained, according to Cal Fire.

Fire crews have continued to make progress containing the blazes aroun Los Angeles, aided by cooler temperatures and much-needed rain. The Hughes fire is now 92 percent contained, and the Palisades fire is 87 percent contained. Containment on the Eaton fire remains at 95 percent.

Cool, wet weather has spread through Los Angeles County, bringing intermittent rain showers and a chance of isolated thunderstorms Sunday afternoon through Monday, with gusty winds and perhaps even some small hail. The National Weather Service posted flood watches because of the risk that rain might fall hard enough to cause flash floods and debris flows in charred areas, especially around the Eaton fire.

Early on the evening of Jan. 7, a resident of a neighborhood of homes backed up against the San Gabriel Mountains in Southern California saw what he described as a bright white light, and then a small fire at the base of an electrical tower up in Eaton Canyon. Another neighbor reported that his lights flickered a few minutes before he saw fire underneath the tower.

So far, many clues to the origins of the deadly Eaton fire, which started in the area just after 6 p.m. that evening and went on to kill 17 people, have pointed to the brushy hillside where a tangle of electrical lines stretch up Eaton Canyon.

Yet Southern California Edison, the utility that operates the electricity infrastructure in much of the Los Angeles region, has said it has no record of an electrical failure on its lines in the vicinity, and that three low-voltage distribution lines in the area had been de-energized long before the fire.

While an official cause is likely to take months for investigators to determine, a growing body of evidence is emerging that suggests the fire started in the dry grasses below a set of transmission towers carrying high-energy power lines. The lines were buffeted that evening by winds that at times reached 100 miles per hour.

A video recorded by a surveillance camera at a gas station less than a mile south of the towers appears to provide an important new clue: Supporting what the residents saw, it shows flashes of light at 6:11 p.m. in the vicinity of three high-voltage electrical towers in Eaton Canyon, and then flames moments later.

The location of the flashes, verified by The New York Times through photographs and videos captured from the same vantage point as the original surveillance footage, could help determine whether power lines played a role in igniting the deadliest of several blazes that are still burning across the Los Angeles area.

The high-voltage transmission lines still had power amid the fire, even though, under Edison’s guidelines, engineers should consider cutting their power when winds exceed 68 to 90 miles per hour.

Edison officials said they had not seen the new video until The Times shared it with them. They urged that it immediately be made available to investigators.

“It requires analysis,” said Kathleen Dunleavy, a spokeswoman for the utility. “This is an ongoing investigation and every piece of information is crucial. We are fully cooperating with the investigation and are committed to a thorough process.”

Neither the video nor any other evidence so far shows conclusively what ignited the fire. But a variety of photos and video from the scene, together with interviews with eyewitnesses, investigators, firefighters and outside experts, all point to a fire that began near the base of one of the utility towers and started to quickly spread.

The issue has enormous implications for who — if anyone — will be held liable for the blaze, which damaged or destroyed more than 10,000 structures and could lead to financial losses currently estimated by Verisk, an analytics company, at as much as $10 billion.

Pacific Gas & Electric, California’s largest utility, filed for bankruptcy protection in 2019 after accumulating $30 billion in liability from years of wildfires. The deadliest, the 2018 Camp fire, destroyed the town of Paradise and led PG&E to plead guilty to 84 counts of involuntary manslaughter.

The parent company of Southern California Edison has seen its stock decline by more than 26 percent this year as questions grow about its potential liability. But California enacted controversial legislation in 2019, championed by Gov. Gavin Newsom, shielding the state’s public utilities from runaway liability following wildfires, and effectively bailing PG&E out in the wake of the Camp fire.

In the days after the fire started, Edison had insisted that there was no evidence to support the idea that a failure of its equipment sparked the Eaton fire.

“We’re not seeing any electrical anomaly until more than an hour after the reported start time of the fire,” Pedro Pizarro, the president and chief executive of Edison International, the parent company of Southern California Edison, said in an interview this month. “And we don’t see any anomaly until an hour, over an hour” after the start of the fire.

Eyewitness reports of a fire around the transmission towers could have resulted from human activity under the lines, Edison officials have said.

One video newly shared with The Times, registered at 6:14 p.m. from a home on Kinclair Drive in the Kinneloa Mesa neighborhood near Eaton Canyon, shows the early stages of a fire directly beneath one of the electrical towers.

Max Belin, whose house has a view of the electrical towers, was the neighbor who saw the flash of light, followed by a small blaze at the tower’s base. Brendan Thorn, the other neighbor, said that when he first saw the fire, it “completely engulfed all four legs of the tower.”

Several sets of transmission towers stand in the hills above Altadena, the unincorporated community northeast of Los Angeles that bore the brunt of the fire’s spread. The Times was able to verify the location of the trio of towers near the fire’s start by matching the 6:14 p.m. video, and others taken around the same time, with the vantage points of eyewitnesses from 10 locations in the surrounding area.

There was discoloration on this group of towers, and metal debris underneath, that were visible days later and was unlike other towers that The Times visited in nearby burned areas.

Whisker Labs, a Maryland technology company with sensors that can detect abnormal activity on electrical wires, detected electrical faults in the general area at around 6 p.m.

Edison’s account has shifted. Initially, in the days following the start of the fire, Mr. Pizarro said there were no electrical problems in the area during the 12 hours before the blaze. But last week, the utility said that while there was not a problem in the transmission lines running through Eaton Canyon, a fault had been measured at 6:11 p.m. at a substation roughly five miles away.

As a precaution, Southern California Edison had cut power to three low-voltage distribution circuits that served Kinneloa Mesa before 4 p.m. on Jan. 7, more than two hours before the reported start time of the fire.

But the utility maintained power on the towering high-voltage transmission lines, each carrying 220 kilovolts of electricity.

Problems during wind events often occur on the much-smaller distribution lines, which typically run on wooden poles and are less resistant to wind than the heavy metal towers that carry high-voltage transmission lines.

But problems have been known to occur on much stronger transmission lines as well. In past fires, transmission equipment has heated up when massive faults occur on these high-voltage lines and they begin to arc, said Robert McCullough, of McCullough Research, a utility consulting firm based in Portland, Ore., who reviewed records and data at The Times’s request.

During arcing, electricity jumps from one place to another, and the lines can dangerously flash and spark. When that happens, the metal on the steel towers can reach temperatures as high as 1,500 degrees, melting pieces of the towers, the bolts on the structures or the aluminum wires. The molten metal drops to the ground and can spark brush fires.

“Arcing can ignite a fire, and that’s obviously going to be largely dependent on what’s underneath that pole at the time,” said Shawn Zimmermaker, deputy chief of law enforcement for the northern region of Cal Fire, the state fire agency. “It would be a cause that investigators would consider, but every potential cause will be looked at.” He emphasized that he was not involved in the investigation.

Cal Fire investigators were seen at the transmission towers on Jan. 14, a week after the fire, combing the area with metal detectors.

The decision by Southern California Edison to shut off power to Kinneloa Mesa, a community of more than 1,000 residents that lost many homes in a 1993 fire, was based on a set of criteria that includes weather forecasts and conditions on the ground, Edison officials said.

“We have rigorous criteria,” Mr. Pizarro said. “What’s the overall risk of the area, the potential for consequence? And then what are the ambient conditions? Let’s say, you know, humidity in the air? What is the moisture or fuel content, you know, around the sites? And importantly, what are wind speeds now?”

Cutting power to a transmission line is a significant step, likely leading to power disruptions over a broad area. So Mr. Pizarro said the threshold for cutting power to transmission lines is high, and Edison never had indication it was needed. “We recognize that there might be something that we just don’t understand right now,” he said.

At least a dozen lawsuits with scores of plaintiffs have already been filed against Edison on behalf of people who have either lost their homes or their lives, presaging a long legal battle ahead.

Last week, a state judge ordered the utility to produce “data from the four low-voltage distribution circuits closest to the preliminary origin area in Eaton Canyon.”

Edison had initially rebuffed efforts to preserve the data, writing in a letter to lawyers that it was “unaware of any information or evidence suggesting that” the company’s “electrical facilities in Altadena may have been related to the ignition of the Eaton Fire.”

In any case, the investor-owned utility is shielded from the full measure of damages under the 2019 law. While the legislation required utilities to establish new wildfire prevention measures, it also created a $21 billion fund that utilities can draw from in the aftermath of fires, if damages exceed $1 billion.

Loretta Lynch, a lawyer and former president of the California Public Utilities Commission, and a longtime critic of the legislation, said the law ensures that California ratepayers and taxpayers will cover some part of liability when fire damages run high, even if utilities are found to be responsible.

“It’s a utility’s dream,” she said.

Arijeta Lajka and Devon Lum contributed reporting.

All they could grab were stuffed animals, toothbrushes, Barbie dolls and blankets. Their bunk beds, cleats and clothes burned with their houses.

The New York Times interviewed 10 children and their parents about what it was like to flee the fires in Los Angeles. They talked about what they are worried about, and what is helping them feel better.

Ivy and Ruby Van Kline are twin sisters who just turned 6 this week. They are in kindergarten at Aveson School of Leaders, a charter school in Altadena, Calif. Their house and school both burned down, so the family moved in with their grandparents.

Jet Crawford, 6, was also in kindergarten at Aveson. He is living in a new house with his mom and his sister, Ilana, 3, after their house in Altadena burned. Their new town is about 20 minutes away from home.

Kurtis Odom, 9, is in fourth grade at McKinley School of the Arts in Pasadena, Calif. His sister, KaylaOdom, is 12 and in middle school. They are living in a vacation rental after their house burned down, and doing school online.

Phoebe Hanelin, 10, is also in fourth grade. Her school, Marquez Charter Elementary, burned down in the Palisades fire. Her home, which was just across the street, is gone. Phoebe’s older sister, Abigail Hanelin, is a sophomore at Palisades Charter High School. Part of her school burned, and now all their classes are online.

Lily Yadegar, Alessandra Santini and Yasmine Santini are friends who also go to Pali High. Lily is 14. Alessandra and Yasmine, both 17, are twins.

Their homes survived, but they spent more than a week evacuated, staying in hotels and rented houses. The three girls wanted to do something for their friends and neighbors, so they started a GoFundMe to help rebuild their school and a donation drive to help their classmates.

Ivy said it was “very, very scary” when the fire came. The power went out. Then the cats started meowing.

“My dad said that our house wouldn’t burn on fire,” Ivy said. “But I just knew right before our house would go on fire, because it looked like the fire was, like, right next to our backyard.”

Kurtis left his house in Altadena in the middle of the night with his mom, older brother and older sister. He could see the fire getting bigger and bigger. Later, they learned that their house was gone.

“I went back to sleep. I woke up. My whole life broke,” Kurtis said.

“I thought we were going to be OK.”

Though Yasmine and Alessandra are twins, the teens responded differently the night of the Palisades fire. Alessandra cried. She packed baby photos and her perfume collection.

She also got the clothes. “We share our clothes majority of the time, even though she doesn’t ask me, and sometimes I don’t ask her,” Alessandra said.

Yasmine brought stuff she thought everyone else would forget about, like medicine and food. “And then I brought my baby blanket and my baby stuffed elephant that I’ve always had,” she said.

Ivy, Ruby and their parents are staying with their grandparents in West Los Angeles. They like that the house is big and has stairs.

“You can go down them and up them, and I could even do splits down them,” Ruby said.

Kurtis and Kayla are doing school online. Their mom decided to keep them home while she figures out where they are going to live. When Kurtis isn’t doing school work, he plays cards with his family and talks to his friends on his tablet.

Jet is staying in a new house with donated furniture. His school remains closed, and his mom is worried. He has autism and had been doing well with the help of his teachers.

Phoebe and her sisters have moved twice since their house burned down. And they know they’re going to have to move again. Abigail is worried about where they’ll go next.

Kurtis worries about everything his family lost.

“Everything is burned down,” he said. He wonders how his mom can afford to replace his soccer cleats and other sports equipment.

His sister, Kayla, says she is shy and worries that she might have to go to a new school. “It’s just going to be awkward for me,” she said.

Ivy and Ruby were excited about their 6th birthday party at Chuck E. Cheese this weekend, where they hoped to see friends from their old school. And Ruby is looking ahead to a milestone at her new school: “Going outside in the big kid area when I’m a big kid and going on the monkey bars.”

Jet’s mom says he has been really upset. When she asked him about the fire, he buried his head in the cushions of their new couch.

“It’s broken,” he said. “Mommy’s house.”

Lily misses driving to school with Alessandra and Yasmine, and stopping at Starbucks along the way.

“Our whole lives, we’ve been looking forward to going to high school together,” Lily said. “It’s just sad.”

Remote learning reminds Abigail of the pandemic, when she was in middle school. This time, it feels worse. Back then, middle schoolers all across the country were in the same boat.

“It was fine in Covid because it was everybody. But now it’s just one school,” she said.

Kurtis will miss the house where he got to know his grandma. His grandparents bought it about 50 years ago after moving to California from Haiti.

Phoebe used to walk to school by herself sometimes. Now she can’t. She likes her new school, but it’s not the same. “Their yard is so small, our yard was giant, so big,” she said.

At Pali High, Lily says everyone knew each other. “I’ve only been there for a semester, and it already feels like a second home to me,” she said.

Ivy and Ruby’s school had a “ginormous playground,” a garden, chickens named Sunshine and Marshmallow and a rabbit named Mr. Fluff.

“I don’t know if they brought the chickens or the bunny,” Ivy said.

Ivy and Ruby’s house was 99 years old. Their dad told them that it had magic from all the people who had lived there and could even grant their wishes.

“But it died, so we have to celebrate it,” Ruby said.

Phoebe and Abigail didn’t have time to grab much. Abigail, who loves to read, took only two books and has already finished them.

But they were able to get all their pets: a dog, two cats, a beta fish, a dwarf hamster and Turbo the tortoise.

“I only brought two stuffies,” Ivy said. “And we brought our toothpaste and toothbrushes and we got our blankets, and we got some of our pillows, and that’s all I brought.”

Ruby brought Barbie dolls. But she is sad because “my bunk bed slide that was ours burned down.”

Kurtis brought his school Chromebook and a tablet he can use to talk to his friends.

“The crazy part is that the trampoline was still standing,” Kurtis said. “And you know what, if the trampoline is standing, I don’t know why the house ain’t standing.”

The Santa Ana winds that have fueled wildfires for weeks in Southern California finally stopped blowing on Friday, and an unusually long period of dry weather was on track to end in Los Angeles County as a cold storm arrived late Saturday.

The system was expected to deliver light to moderate rain that will fall intermittently through Monday. The weather will give the arid landscape and withered vegetation a much-needed soaking and benefit firefighting crews.

Still, the forecast showed a small risk that bursts of heavy rain could cause flash floods and mudslides around areas of Los Angeles County recently scarred by wildfires, including the northwest (Hughes fire), east (Bridge fire), southwest (Franklin and Palisades fires) and especially the central area where the Eaton fire burned.

The National Weather Service issued a flood watch for those areas from 10 a.m. Sunday to 4 p.m. Monday, when there is the highest chance for rain and risk for thunderstorms.

Kristan Lund, a meteorologist with the Weather Service, called flooding the worst-case scenario for the conditions in Los Angeles, where there is up to a 20 percent chance that debris flows could damage roads and structures.

“What we’re telling people is to avoid the area during the watch period,” Ms. Lund said. “Use sandbags to protect your property, and if residents decide to stay, make sure to stock up on supplies in case road access is blocked.”

The Los Angeles area has seen its driest start to the rainy season on record and has not measured significant rainfall since last spring. Since May 1, the Weather Service’s gauge in downtown Los Angeles has measured just a little more than a quarter-inch of rain. This weekend’s expected storm has the potential to bring nearly four times that amount.

The burn scars in Los Angeles County, where trees and brush were devoured by flames, are most likely to benefit from the rain. “If we get gentle rains, it’s going to help make those burn areas recover and re-vegetate,” said Jayme Laber, a hydrologist with the Weather Service.

The first drops of rain began to fall Saturday night, with showers expected to increase Sunday into Monday. Most locations across the county, including downtown Los Angeles, are expected to record up to an inch of rain in the storm.

But isolated showers and thunderstorms could bring rain that falls at three quarters of an inch an hour, and the heavier rains could lead to debris flows Sunday afternoon through Monday afternoon. The thunderstorms could also kick up strong, damaging winds, drop small hail and cause water spouts over the ocean, the Weather Service said.

The weather is expected to temporarily lower the risk of wildfires, but this one storm won’t fully end it.

“It’s only going to help things out for a couple weeks,” Matt Shameson, a meteorologist with the U.S. Forest Service, said of the storm. “If we get another one or two decent systems, that will help us out significantly.”

The good news is that another set of showers could come over the region sometime next week, Mr. Shameson said.

Even before the devastating wildfires, Hollywood was struggling.

Squeezed by studio cutbacks and competition from other states and countries, film and television production in the Los Angeles region had already fallen to a near-record low last year, imperiling the livelihoods of not just casts and crews but also the caterers, drivers and many others who depend on the entertainment industry. Some, seeing their work dry up, were leaving for other states that have lured productions with tax credits.

Then the fires swept through, dealing yet another blow to a region, and an industry, that had been buffeted in recent years by a pandemic and then strikes that halted production amid a rapidly changing entertainment landscape. The Southern California fires have given new urgency to efforts by state and local officials to keep Los Angeles a place where films and television shows are made, and not just greenlit by studio executives to be shot elsewhere.

At stake is the future of a defining industry that helps make Los Angeles a vibrant creative capital, employing tens of thousands of workers in a wide variety of fields — people like John W. Rutland, a cinematographer, and his wife, Marta Gené Camps, a television writer.

Just a week before the fires the couple had been looking over their mortgage documents. They wanted to reassure themselves that even though work had grown sparse, the equity in their three-bedroom home was on the rise. Then the Eaton fire rampaged through the eclectic art hamlet of Altadena, burning their pet chickens, destroying their home and leaving them with “a worthless strip of charred land,” as Rutland described it.

“Who knows when it’ll be safe to come build again?” asked Rutland, 44. “And if we want to build again?”

As Los Angeles begins to think about how to rebuild homes and whole neighborhoods that were reduced to rubble, officials are renewing their efforts to revive local film and television production. Even after recent setbacks, the region remains the business’s epicenter. The entertainment industry contributes more than $115 billion annually to the regional economy, local officials estimate, and helps sustain 681,000 jobs in a wide variety of fields.

But things have not been going well for some time. Still reeling from the long shutdowns and extended periods of unemployment during Covid, the business ground to a halt for another six months in 2023 when the writers and actors went on strike.

After production resumed, studios retrenched, effectively ending the peak television era. The number of television series produced in the United States last year fell for the second year in a row, and are down 23 percent since 2022, according to a study by Luminate.

The slowdown has had a big impact in Los Angeles. Location shoots in the region fell last year to its second-lowest total on record, behind only 2020, the year the pandemic stopped work, according to FilmLA, the film permitting office. The number of location shooting days in the region has dropped 40 percent since reaching a high in 2016, according to data from the office. Reality TV has seen an especially steep decline, it reported.

The fires underscored how few major movies are being filmed in Hollywood these days. When the blazes erupted, only two movies from major studios were affected — because only two movies were shooting in Los Angeles at the time.

Local officials said Los Angeles was losing productions to other nations and other states, including Georgia and New Mexico, which have wooed them with generous tax incentives. A survey by the The New York Times last year found that 38 states offer such incentives, and have spent more than $25 billion attracting productions over the past two decades. Most economists consider such subsidies a poor investment for states, but the programs continue to be popular with legislatures and studios, and have lured many productions from Los Angeles.

“More and more jurisdictions have come online to compete and take business away from L.A. and the U.S., and they’re broadening what’s eligible for those credits or refunds,” said Paul Audley, the president of FilmLA.

While Los Angeles County had 35 percent of the nation’s film and television jobs before the 2023 strikes, its share dropped to 27 percent afterward, according to a recent report from Otis College of Art and Design.

California has its own tax credit program, which offers $330 million a year in incentives, but state and local officials say that is not enough to remain competitive. In October, Gov. Gavin Newsom proposed more than doubling the funding to $750 million annually.

Colleen Bell, the state’s film commissioner, said that expanding the credit was essential, and that she often had to turn away projects because the program was oversubscribed.

“The truth is, people want to shoot in California,” she said. “I hear this over and over and over again, the depth and talent of our crews, our equipment, innovation, our infrastructure.”

Last week thousands of people in the entertainment industry signed the #StayinLA petition, calling for uncapping the state’s tax incentive program for the next three years for projects that shoot in Los Angeles County, and calling on studios and streamers to pledge to increase local production by at least 10 percent during that period.

This month the Los Angeles City Council approved a $1 billion project to build and enhance sound stages and production facilities at the Television City complex at Beverly Boulevard and Fairfax Avenue. Mayor Karen Bass of Los Angeles, who supports increasing the state tax credit, is planning to meet this week with a council of entertainment industry leaders to discuss keeping more productions local.

But many workers in the industry who have seen jobs dry up say they now face a choice: keep hanging on in the hopes that things turn around, or try something new. And those who lost their homes in the fires could be forced to decide soon.

The International Alliance of Theatrical Stage Employees, which represents a wide range of professionals including makeup artists, set decorators and animal wranglers, said that at the peak of the crisis, 8,100 of its members were in evacuation zones. At least 300 lost their homes. “Pretty devastating,” said Michael Miller, a union vice president.

Marco Cordero, 42, a director of photography, was among the workers stressed by the shrinking job market even before his home in Altadena was destroyed.

“We all know so many people that haven’t worked a very long time, that are either leaving the industry, considering doing so or moving somewhere else, where the cost of living is lower,” he said, “because the amount of work that was here to support them isn’t here anymore.”

Adrienne McDonnell, 46, a makeup and special effects artist, and her husband, BJ McDonnell, 49, a director and camera operator, lost their house in the Sunset Mesa neighborhood of Malibu.

“Everybody was starting to see the light at the end of the tunnel,” she said. “Negotiations are done, the strikes are done. Newsom is going to finance some incentives for us to get filming back here. We were all hopeful — and then this happens.”

The loss of so many homes and the skyrocketing cost of housing in the region could be the last straw that pushes some workers out of the state, or even the industry.

But nearly a dozen members of the film and television industry who lost their homes said in interviews that they plan, at least for now, to stay and rebuild.

Many said they have been overwhelmed by the support they received. When Olivia Newman, the director of the upcoming film “Remarkably Bright Creatures,” lost her home in the Eaton fire, Netflix set her family up in a home in Vancouver, British Columbia, where the movie is being made.

Unions set up pop-up donation centers with everything from basic supplies to opportunities to meet with emergency resource officials. Fire victims said it had become clear their support system was in Los Angeles.

Others worry that they may not be able to afford to leave, if their insurance is not enough to pay off their mortgages, or if doing so would leave them with no savings. Some said their losses had granted them a moment to contemplate what they wanted their futures to look like.

“Is this our get-out-of-jail-free card?,” the cinematographer Gabriel Patay, 40, said he wondered after he and his wife, a documentary producer, lost the home they spent nine years restoring.

“We are tied to this property, we are stuck in L.A.,” he has thought. “Should we leave?”

Patay is cleareyed that his insurance will not cover the cost of rebuilding. He and his wife are looking into mortgage deferment and recently applied for hardship status with their bank.

Job opportunities have not been robust either. Patay recently finished work on a documentary for Hulu, but described current job prospects as “bleak.” Now the couple is considering rebuilding their home, slowly over time, if they can somehow make the economics work.

Some have rethought their futures in other ways.

Madeline Power, a 32-year-old producer, had been just about ready to leave Los Angeles before the diaster.

With no work, the past 12 months had been “the worst financial year of my life,” she said, noting that she took odd jobs babysitting and cleaning. She felt, at times, like the city itself was rejecting her.

Then her house burned down. She found purpose using her skills as a producer to help raise money for her neighbors, and when people heard of her situation, some came to her with job leads. Now she, too, has $30,000 in donations — more money than she says she has ever had.

There is no question in Power’s mind. She is staying.

“L.A. caught me,” she said. “L.A. came and just showed up.”

John Koblin contributed reporting from New York and Alyce McFadden from Los Angeles.

The rain that is expected to hit the scorched Los Angeles landscape this weekend may bring relief to the fire fights, but it could also bring flash floods and mudslides. Although forecasts show that the risk is relatively low, local officials are taking the warnings seriously.

Mayor Karen Bass of Los Angeles, who has faced criticism for her handling of the crisis, issued an emergency order earlier this week, mandating that city crews clear out vegetation and reinforce roads ahead of the rainfall.

Crews were also directed to install concrete barriers, lay sandbags and clear debris across burn scars and fire-affected neighborhoods in the hopes of stemming large flows of water.

“These communities have already endured unimaginable loss,” Mayor Bass said in a statement. “We are taking action against further harm.”

Mudslides, also known as debris flows, can occur when burned and dry soil becomes compacted like concrete. Water then funnels down slopes that have lost vegetation that would normally slow or absorb it. The resulting rushing water can carve up the landscape, uprooting trees and dislodging rocks, brush and anything else in its path.

At a news conference this week, Mark Pestrella, the public works director for Los Angeles County, said that people living on or near scorched hillsides should be cautious, especially if their homes had not been inspected after the fires.

“Your best bet is not to be in that home when it rains,” Mr. Pestrella said.

Residents can use burn maps created by the U.S.G.S. to determine if their homes are at risk. For those in potential flood areas, free sandbags are available at fire stations.

Austyn Gaffney, Amy Graff and Jesus Jiménez contributed reporting.

The massive fires have devastated communities in the Los Angeles area, burning thousands of homes and forcing the evacuation of more than 100,000 residents at one point.

Aid organizations say they are thankful for all the help that has poured in after the fires broke out almost two weeks ago — but there’s still more to be done. For those looking to help, it can be overwhelming to know where to start and what is the best way to provide assistance. And with the recent proliferation of online scams and fake donation sites, it can be difficult to ensure that a donation will go to the right place.

Money is often the most useful donation, giving organizations helping victims the flexibility to purchase exactly what is needed and use resources efficiently.

For example, Christina Bragg, a spokeswoman for the Y.M.C.A. of Metropolitan Los Angeles, said a family housing fire evacuees requested a portable toilet. The organization didn’t have any on hand, but with funding, it was able to provide one that included a shower for the family.

Those looking to give money directly to victims can consider platforms like GoFundMe, which has raised over $200 million in the Los Angeles fires. GoFundMe set up a page with verified fund-raisers supporting survivors and details on its wildfire relief fund, which provides emergency grants.

GiveDirectly, a nonprofit offering unconditional money transfers, is also collecting donations for low-income fire survivors. The organization uses fire damage and income data to identify the communities in need the most, and then enrolls and pays survivors through an app used to manage food stamp benefits, according to Tyler Hall, a spokesman.

Physical donations, like clothing, shoes and toys, can create logistical challenges for aid organizations, including the costs and time required to sort, store and transport items that may not match survivors’ needs.

Evan Peterson, a spokesman for the American Red Cross, recommended calling 211 or visiting 211la.org/LA-Wildfires to confirm which organizations are accepting items before collecting or dropping off donations.

Clothing donations, in particular, have overwhelmed some groups. “We have a warehouse full of extra things, and most of it is clothes,” said Ms. Bragg of the YMCA, which provides on its website a list of most-needed items, including baby formula, cereal and air purifiers.

It’s important to verify the legitimacy of any aid organization before donating. Scam sites and accounts often arise after natural disasters, and California officials leading the fire response efforts have warned people of such schemes.

Resources like Charity Navigator and GuideStar provide evaluations and information on nonprofit organizations. The Federal Trade Commission also offers tips for identifying fake charities and fund-raisers.

While many organizations are addressing immediate needs, some are also focusing on long-term recovery, such as rebuilding efforts and mental health support.

For example, the nonprofit Direct Relief has been distributing free N95 respirators and other essential items for short-term aid, but it is also providing grant funding to organizations assisting with the long-term physical and mental health impacts of the fires, according to Brea Burkholz, a spokeswoman.

As with immediate relief, financial donations can significantly help with long-term recovery efforts.

Bishop Wash, a spokesman for the Salvation Army, said that monetary donations “will continue to be used in those long-term relief efforts, months or even years down the line.”