Two morning earthquakes with magnitudes of at least 3.5 struck near San Francisco on Friday and Sunday, according to the United States Geological Survey. A 3.5-magnitude earthquake near Concord in the East Bay shook the area on Sunday, two days after a quake of similar magnitude struck in the Pacific Ocean off the coast of San Francisco on Friday, data from the agency shows. Residents across the region reported mild shaking but no immediate damage from either earthquake. U.S.G.S. data for both earthquakes earlier reported that each one was as strong as a magnitude 3.7 quake. As seismologists review available data, they often revise the earthquake's reported magnitude and update shake-severity maps. The location of Friday’s earthquake recalled one of the biggest earthquakes of all time, a 7.9-magnitude quake that nearly destroyed San Francisco in 1906. Friday’s quake, and its much more powerful relative, likely both occurred along the San Andreas fault, said Robert Skoumal, a research geophysicist at the United States Geological Survey. Preliminary location data from the U.S.G.S. suggested that the two may have shared more than a fault line — both occurred at very nearly the same location, about two miles west of Golden Gate Park. Mr. Skoumal said it was not possible to determine with certainty whether the two quakes shared precisely the same epicenter because of changes in measuring techniques over the last century. “Back in 1906, we didn't have the best seismic instruments out there,” he said. Earthquakes of similar size are also fairly common in the area west of San Francisco, he said. “We've had dozens of magnitude threes just over the past several decades along this one little patch,” he said. And while the risk of earthquakes in the San Francisco area is serious, Friday’s small earthquake did not signal the imminent arrival of a more destructive quake, he said. “I wouldn't say this particular earthquake should make anyone worried,” Mr. Skoumal said. Aftershocks in the region An aftershock is usually a smaller earthquake that follows a larger one in the same general area. Aftershocks are typically minor adjustments along the portion of a fault that slipped at the time of the initial earthquake. Aftershocks can occur days, weeks or even years after the first earthquake. These events can be of equal or larger magnitude to the initial earthquake, and they can continue to affect already damaged locations.

More howling, whipping, fire-stoking winds have arrived in Los Angeles. They are expected to strengthen by dawn and may blow up to 70 miles per hour. Some gusts could rekindle parts of the major blazes tearing through the city’s hills and suburbs. Others could start new fires. It may seem hard to understand why the combined resources of the federal government, California and Los Angeles haven’t been able to defeat the wildfires after a week of fighting them. The winds are a major reason. The gusts hurl embers across great distances, spreading fire quickly and thwarting efforts to pinch it off. Planes and helicopters that spray water and flame retardant can’t fly. Firefighters on the ground can’t battle the flames on streets and hillsides without fear they’ll be incinerated. At their peak, the winds have forced firefighters to focus on something else: evacuating residents. “You’re just trying to keep people alive,” Lenya Quinn-Davidson, a fire expert in Northern California, said. How to stop a fire When forests and grasslands ignite, crews follow a strategy called anchor and flank. They find a safe spot, or anchor point, upwind of the blaze. Then they attack from the edges: They douse the flames with hoses and remove anything flammable from the fire’s path. They use power tools to thin the vegetation or — for the bigger stuff — reduce it to ash with small controlled burns. That’s called a fire line. The advancing blaze stops when it reaches the fire line and finds nothing else to consume.But it’s incredibly hard to anchor and flank in strong winds. Even a spot that seems safe won’t remain safe for long. Flying embers can soar miles away from the fire’s front, meaning the danger spreads too quickly for firefighters to keep up. “Fires under these conditions — they’re not moving on the ground” as a normal fire would, said Hugh Safford, a fire ecologist at the University of California, Davis. “They’re moving in the air.” That’s why some wildfires in Southern California can’t be stopped until the desert winds, known as the Santa Anas, recede. Advertisement SKIP ADVERTISEMENT Urban warfare The Los Angeles inferno adds another difficulty: an urban tinderbox. When embers float from home to home on a crowded street, there’s no way to create fire lines to interrupt the flames. “All of the things that we have in our houses — drapes, couches, carpet — all of a sudden that stuff can ignite really rapidly,” Rick Connell, an officer with the U.S. Forest Service, said.And winds don’t just ground firefighting aircraft. They also make the water and fire retardants they spray less effective. Gusts turn the liquid into mist by the time it hits the ground, where it does little to smother the blaze. Even in the best circumstances, retardants can do only so much. “If you’ve already got 100-foot flames, you’re just wasting money,” Connell said. Over the last week, Los Angeles deployed more firefighters and received additional air support, including from the military. “We’re absolutely better prepared,” the county’s fire chief told reporters on Monday. But the experts I interviewed said it would be unrealistic to expect fires of this size to be contained in just a week. For now, the best hope may be to wait until the current winds slow down.

Meteorologists get it wrong sometimes. Thankfully, when they got a Los Angeles weather forecast wrong this week, it was because the winds were weaker than predicted on Tuesday and no longer met the National Weather Service’s criteria for a “particularly dangerous situation.” The phrase describes a rare, high-level warning that is meant to be used only every few years for the worst possible wildfire conditions of dried vegetation, low humidity and strong winds. Just a week ago, at the start of a cycle of four Santa Ana wind events that have overtaken the region since then, the forecast warned of a “particularly dangerous” wildfire outlook, with a windstorm of a strength not seen in over a decade. That forecast was realized when the Palisades fire, the Eaton fire and other blazes sent Los Angeles residents fleeing from their homes as a torrent of winds pushed fires raging through their neighborhoods.Weather Service meteorologists make their forecasts based on a combination of current conditions, historical events and computer weather models. They take all this information in and then forecast what they think is the most likely outcome. There are always outliers, conditions that could occur but are less likely. Sometimes, a storm will overperform the forecast, and sometimes it will under perform. In meteorology, both eventualities are considered “busted forecasts.” While forecasters who predict an especially extreme event might be happy if the conditions aren’t as bad as they had predicted, they know that if the forecast is off by too much, people will trust future warnings a little less. James Brotherton, a meteorologist with the Weather Service in Los Angeles, said he would much rather have a forecast be wrong if it meant there was “less pain and suffering.” Ahead of this cycle of winds, forecasters put another “particularly dangerous situation” warning in place from 4 a.m. Tuesday through noon on Wednesday, as they feared more strong winds would help fuel existing fires and possibly spark new ones. But by early Tuesday afternoon, the winds were proving to be less strong than expected, and the Weather Service dropped the warning for the rest of the day. The move was temporary, and another “particularly dangerous situation” warning will be in place from 3 a.m. to 3 p.m. Wednesday. Ryan Kittell, another forecaster in the Los Angeles office, compared it to someone filling out an N.C.A.A. bracket every March. “Even if you’re the best, at some point you won’t have a forecast verify as you would like,” he said. The “particularly dangerous situation” designation is still a relatively new tool, Mr. Kittell said. Tuesday’s forecast was always right at the line between high level and not, and the office opted to use the stronger warning because of the ongoing fires across the region, he said. Robert Clark, a fire behavior analyst for Cal Fire who is working on the Palisades fire, was relieved Tuesday’s winds weren’t as powerful. The fire didn’t grow overnight, and quieter weather was allowing crews to extinguish fire in pockets of smoldering landscape and vegetation. While conditions have improved, Mr. Clark said he was most concerned about the forecast for the Santa Ana winds to pick up again Tuesday night into Wednesday. “And then we’re looking out to the future to see what happens with the weather forecast with an additional round of Santa Ana winds possible next week,” he said.

Los Angeles residents are facing another round of fire danger as gusty Santa Ana winds were expected to intensify once again over the next few days. The National Weather Service had warned these winds could lead to “explosive fire growth,” prompting forecasters to issue rare, “particularly dangerous situation” warnings for parts of Ventura and Los Angeles Counties for Tuesday and Wednesday. But by early Tuesday afternoon, the winds were proving to be a little weaker than anticipated, prompting the Weather Service to temporarily drop the dangerous situation designation. They believe winds may pick back up again, though, so the warning will go back into effect on Wednesday from 3 a.m. to 3 p.m. Key things to know about the forecast Though Tuesday’s winds were less strong than anticipated, they were still powerful, and red flag warnings remained in effect. A “particularly dangerous situation” warning, one of the strongest the Weather Service has in its arsenal, will be in effect again from 3 a.m. to 3 p.m. on Wednesday. A weather system moving in on Thursday is likely to bring conditions that will help firefighters in their efforts to gain control of the blazes, but forecasters warned of another possible wind event early next week. The region remains critically dry and is not expected to see significant rainfall until at least next month. By Tuesday afternoon, the strongest sustained winds were moving through Ventura County valleys at nearly 30 m.p.h., and while the mountains had seen gusts reach over 70 m.p.h. The winds were generally lighter than the worst-case scenario that forecasters had anticipated, but they warned there could still be a more significant increase in wind speeds on Wednesday. The Weather Service began using the “particularly dangerous situation” red flag warning in recent years to alert firefighters to types of conditions where fires are more likely to spread, said Todd Hall, a meteorologist at the Weather Service in Los Angeles. The intention had been to use them once every three to five years, he said; two have been issued in the last week. In addition, across the wider region, longer-term warnings for fire weather from the Weather Service’s Storm Prediction Center have been upgraded to “extreme,” the highest classification. In areas such as Ventura Valley and the San Bernardino Mountains, wind gusts exceeding 50 m.p.h. will combine with extremely dry air to create hazardous conditions from through Wednesday.

If you’re tracking wildfires or the weather conditions that make them possible, you may have come across some terms you don’t recognize. Here’s what they mean. Watches and Warnings Fire watches and warnings are issued by the 122 local National Weather Service forecast offices across the United States. Forecast offices maintain criteria specific to their areas of coverage that are developed in consultation with land and fire managers, the federal, state or other bodies — such as the U.S. Forest Service — that study a particular place’s vulnerability to fire. The criteria used to determine whether a local forecast office issues a watch or a warning can include, among other factors, the likelihood of lightning (which can ignite a fire), high winds and low humidity.Watches and warnings don’t predict wildfires, but they do predict the conditions that are conducive to their formation or spread. They can take two forms: Fire weather watch: This alert is issued when there is a “high potential for the development of a Red Flag event” in 18 to 96 hours. “The overall intent of a fire weather watch is to alert users at least a day in advance for the purpose of resource allocation and firefighter safety,” according to Weather Service policy. Red flag warning: This more serious alert describes an “impending, or occurring Red Flag Event,” indicating “a high degree of confidence that weather and fuel conditions consistent with local red flag event criteria will occur in 48 hours or less.” The term has been used by the Weather Service and the National Oceanic and Atmospheric Administration since the 1960s, according to a NOAA fact sheet. Fire weather watches and red flag warnings can be issued several times a year, in some cases in quick succession during a single weather event, in fire-prone areas, said Robyn Heffernan, a fire weather services senior adviser at the National Interagency Fire Center.Much more rarely, forecasters can advise of a “particularly dangerous situation” within a forecast, she added. This kind of description is made “if an office feels like this is an extreme event where the criteria for issuance is greatly exceeded, or we’re near record levels or at record levels,” Ms. Heffernan said. Before this fire season, the Weather Service’s Los Angeles office had used that designation only twice, both for warnings in 2020. Since November, it has issued them four times. Fire Weather Outlooks The Storm Prediction Center, a part of the National Weather Service that monitors for severe weather events like thunderstorms, tornadoes and winter weather, also identifies areas where there is a “significant threat for the ignition and/or spread of wildfires” in the near future, according to a description of its products published by NOAA. Fire weather outlooks are broader in scope and are intended to provide guidance for forecasters and to “aid land management agencies in determining large-scale areas of fire danger risk,” according to Weather Service policy. They are not warning products, Ms. Heffernan said. Advertisement SKIP ADVERTISEMENT The Storm Prediction Center describes five kinds of fire risk. For the center to label an area with a given risk level, the area must satisfy several criteria for weather and the potential for fueling fires. The first three pertain to how actively a fire may burn: Fire weather risk is described as “elevated” when “we know that the fuels are dry and that the weather is conducive for fire activity,” Ms. Heffernan said. Fire weather risk is described as “critical” when “we know that if a fire starts in that area, it is going to be difficult to contain,” she said. Fire weather risk is described as “extremely critical” when “there are going to be very limited fire tactics that are going to be able to be employed on that fire because the weather is so overwhelming,” such as during a Santa Ana wind event, she said. There are also two risk levels that pertain to the potential for a new fire to be ignited (it would be rare, though not impossible, for the two types of fire risk to coincide, Ms. Heffernan said): An outlook of “isolated dry thunderstorms” is issued based on the whether a potential fire has fuel to spread (determined through drought, rainfall and vegetation data, for example) and the presence of isolated cloud-to-ground lightning strikes, according to Weather Service directives. This is equivalent to an elevated fire weather threat. An outlook of “scattered (critical) dry thunderstorms” is issued based on a potential fire’s fuel conditions and the presence of scattered-to-numerous cloud-to-ground lightning strikes. This is equivalent to a critical fire weather threat.

I’d like to put forth January for worst month of the year. February requires you to trudge through only 28 or so frigid days, with the promise of spring on the other side. December had parties and procrastination and excuses to suspend conventions like meals per day (third dinner) and portion size (a cocktail fit for Ina Garten). In January, you’re staring down 31 bleak days, the legal limit, with no hope of things turning around any time soon. Ideally, I’d like to see January wiped off the calendar, but one must endure it. Over the years, from my berth in the Northeast, I’ve developed a survival guide to ensure I make it to Valentine’s Day. Start with your hands, which I trust look terrible by this point. I categorize hand creams in progressive levels, similar to the DEFCON model of military readiness. We begin with Level 3: an everyday variety from the likes of Jergens or Lubriderm, moisturizing yet light enough to be swiftly absorbed into the hands, so you can apply it and then leave your home. Then again, how many times are you actually leaving your home in January? Proceed to Level 2, where you have options: a neon green tub called O’Keeffe’s Working Hands, or a slightly darker green tube called Weleda Skin Food. The names signal we’re getting serious. They’re heavy enough to take some time to sink in, but not so incapacitating as to prevent you from scrolling fantasy flights to Miami. The pinnacle, Level 1, can be applied only right before bed, or any time you get that January feeling of “It would take an actual DEFCON 1 situation [imminent or current nuclear war] to get me to leave this spot on my couch.” That’s the occasion for Eucerin Original Healing Cream, spackle for the skin. Apply to your hands, your elbows, probably not your feet — they’re simply too far gone. Wear socks until spring. Do not move until the thick white goop recedes into your sad winter skin. It could be days. A joke about Go-Gurt from an old Ellen DeGeneres special comes to mind. “Was there a big mobility problem with yogurt before?” she asks, then mimes picking up the phone and receiving an invitation from a friend. Moments later, spirits falling, she remembers she’s just opened a traditional yogurt that must be eaten with a spoon. Having committed to the complex task at hand, she obviously can’t make the date. Eucerin Original Healing Cream is the yogurt-with-a-spoon of January. As Ms. DeGeneres says, you’re in for the night. Apply when your skin is very dry, or when you have a social event you want an excuse to bail on. The next part of my survival guide is medically ill advised, but I’ll tell you about it anyway. It starts with a space heater recommended by a trusted website, which worked well, except for the part when it shot out sparks in my kid’s room. Or did it? I willed myself to forget the maybe sparking — so chilly in there! — until my husband plugged it in one day, smelled the singe and observed the cord melting. Then all the lights in the house went out. I imagine the blown circuit was for the best. While he trod down to our basement, I did the cost-benefit analysis: warmth versus risk of death. I came out somewhere in the middle. Now I use our other space heater only when I’m alone and in my office, so the danger is confined to me. My husband and children will live on, and they’ll be chillier for it.Space heaters are conventional, though. My greatest achievement, while it lasted, was my heating pad. It felt so innovative — how many people use a heating pad for daily warmth, comfort and, if I’m being honest, some degree of companionship? I researched and ordered and returned until I found what I was looking for: a medical-grade device that probably shouldn’t be legal in the United States. This thing gets hot, especially if you remove the outer covering to reveal the inner layer emblazoned with a warning that says in all caps, “Never use pad without cover in place.” I ignored this. I mainly wrapped the delicious heating pad around my hands. Four Januarys ago, I developed a condition called chilblains, which is when your fingers basically cease to function in response to cold. It’s grim. Your digits feel like ice. They swell, then split. Then things get really gross. My husband thought I must have accidentally shut my hand in a door. The dermatologist told me it was chronic. But he didn’t know about the power of my 75-watt heating pad. I carried that thing around the house. When it started acting a little wonky I bought two more as an insurance policy, bracing for the inevitable day it would be banned domestically. My skin condition was in remission for two winters. I was sure I’d bested it. I’m not sure why this January has done me in already. Was it our new puppy, who requires me to wrest off my mittens and face the elements approximately 800 times a day as we try, and fail, to house train her? Was it karma for flagrantly removing the heating pad’s outer cover? Whatever the reason, the cold and swelling returned to my fingers. I ramped up use of my heating pad in turn. Simultaneously, I began to develop a spiderweb-like rash on my thighs. It lit up red in the shower. I connected the rash to the fact that the heating pad sits squarely on my lap while I’m treating my fingers, but I didn’t really care — until my husband, a physician, informed me I might be doing permanent damage. Advertisement SKIP ADVERTISEMENT It seemed I had given myself a new condition, the evocatively named toasted-skin syndrome. A different dermatologist (on Instagram this time) told me it was forever. I unplugged the heating pad but couldn’t stop eyeing it. My fingers were so cold. I started to feel that there were only bad choices: Heat away the chilblains and give myself toasted-skin syndrome, or leave my fingers to wilt and preserve my milky thighs. I made it two days before plugging the heating pad back in, cursing myself for throwing out the protective cover years ago. A while back, the cartoonist Roz Chast drew a New Yorker cover that represents a January calendar. Each day contains a typical seasonal entry. “Lose keys in snow.” “Slip on ice.” “Still January.” (That last one’s on Jan. 3.) Jan. 31 resembles a giant yellow sun, flagged with stars, labeled “Last day of January!” I framed the cover for my office, where the space heater’s still chugging.

Winds picked up again early on Sunday across Southern California, reaching close to 70 miles an hour near the western and eastern San Gabriel Mountains and the Highway 14 corridor. By the afternoon the winds are forecast to ease for a while, giving firefighters a reprieve to battle devastating wildfires. But that reprieve might not last long, forecasters say, as another round of strong, gusty Santa Ana winds develops on Monday and Tuesday, contributing to another stretch of dangerous and potentially extreme fire conditions. Brian Hurley, a meteorologist with the Weather Prediction Center of the National Weather Service, cautioned that while the winds this week may not be quite as strong as they were last week, their long duration could make the fire risk worse, especially in the western Los Angeles basin and Southern Californian mountains. With the humidity remaining low and the vegetation in the region very dry, an upgrade to “extreme” fire conditions, the highest risk classification, is “very well on the table,” Mr. Hurley said. Conditions were rated extreme last week, when wind gusts reached 100 m.p.h. For now, though, the fire risk is expected to be one level lower, at “critical,” in parts of Southern California from Sunday afternoon to Tuesday afternoon. The National Weather Service office in Los Angeles forecasts that the stronger Santa Ana winds will last from Monday night into Wednesday. Andrew Rorke, a meteorologist with the Weather Service, said the winds were expected to follow the typical Santa Ana direction, blowing northeast to southwest. The areas with the strongest winds will stretch from the mountains northeast of the Santa Clarita Valley, through the valleys along the Ventura and Los Angeles county line, and out across the western Santa Monica Mountains. They will be most powerful in the mountains, with gusts up to 60 m.p.h. Areas at lower elevations like San Clarita Valley and parts of Los Angeles and Ventura Counties will experience wind gusts between 35 m.p.h. and 55 m.p.h. “The only good news here is that the San Gabriel foothills and Eaton Fire area will not see any strong winds from this event,” Mr. Rorke said. Looking ahead, forecasters predict that the winds will continue into Thursday, but be weaker than on Wednesday, and may fall below the levels at which they would prompt a fire risk advisory. This will also lower temperatures in valleys and along the coast. By Friday, a dry weather system will move east, and the winds will shift to blowing onshore from the ocean, dropping temperatures a little further. One glimmer of hope, Mr. Hurley said, is a break from the extreme fire danger later in the week, when increased humidity is expected along with the lighter winds. “There’s a very small chance of rain next weekend, but that’s going out a bit, and it’s not a whole lot of rain in the forecast,” he said.

The focus this week has been on how extreme winds have fueled the most destructive fires in Los Angeles’s history. But that’s not the only concern. On Friday, even as slowing wind speeds increased hopes that firefighters would contain the blazes, dry vegetation and steep terrain pushed the Palisades fire, the biggest, east, putting a new swath of Los Angeles under mandatory evacuation orders. The blaze was burning along the tops of the ridges of Mandeville Canyon, said Kenichi Haskett, a division chief with the Los Angeles County Fire Department, on Friday night. The fire tore through a steep area full of dry vegetation and threatened the neighborhood of Encino in the north. The spread was being driven by the landscape rather than wind, Mr. Haskett said. “We’re not getting strong winds the way we got on Tuesday and Wednesday.” The Palisades fire has now burned more than 21,000 acres in five days. The rains that usually fall in autumn and early winter did not come, leaving most of Southern California bone dry and leaving vegetation primed to burn. Most locations south of Ventura County have recorded about a quarter-inch of rain or less in the past eight months, while the Los Angeles area has received only sprinklings of rain since April. That means the Santa Ana winds, the strong, dry gusts that have driven the wildfires, have had a particularly dramatic effect. Even as they have subsided, the parched vegetation has continued to fuel the Palisades fire, experts said. Stronger winds are expected to return to Los Angeles and Ventura counties Saturday afternoon, reaching the highest speeds overnight into Sunday morning and heightening the risk of rapid wildfire spread. Wind speeds over the fire were light — under 15 miles per hour — on Friday night, said Dave Gomberg, a meteorologist with the National Weather Service. In comparison, Wednesday saw wind gusts of over 90 m.p.h. “I think a big component is the fuels are exceptionally dry,” Mr. Gomberg said of Friday’s expansion. The Palisades fire was “following the terrain and the fuels,” said Craig Clements, director of the Wildfire Interdisciplinary Research Center at San Jose State University. Fires thrive in hilly terrain and move faster uphill than downhill, he said, adding, “The steeper the terrain, the faster the fire can go.” The fire chewing its way through Mandeville Canyon is a “plume-dominated fire,” that is being fueled by its own wind, said Redondo Beach Fire Chief Patrick Butler, a former assistant chief for the Los Angeles Fire Department who has led the response to many Southern California fires. Such blazes often shoot upward and then collapse, scattering embers for miles in concentric patterns, he said. On Friday evening, ash was falling in the Brentwood neighborhood to the south of the canyon. Wildfires are notoriously hard to fight in Mandeville Canyon, which has poor radio communication and an extremely narrow road, Mr. Butler said: “There’s basically one way in and one way out.”

The alert came in blaring, hot-pink, all-caps: Be prepared for a “LIFE THREATENING & DESTRUCTIVE WINDSTORM!!!” The notice on Monday was one in a series of warnings issued by the National Weather Service about the powerful Santa Ana winds that were about to blow through Southern California, which hadn’t seen serious rain in months. Officials in Los Angeles, a city that is accustomed to treacherous fire conditions, turned to a well-worn playbook. The city predeployed nine trucks in vulnerable areas and called in 90 extra firefighters. The county fire department moved 30 extra engines into the field and called up 100 off-duty firefighters. The U.S. Forest Service brought in trucks and support units, as well as bulldozers, helicopters and planes. But by Tuesday afternoon, five hours after a fire ignited high in a canyon in the oceanside Pacific Palisades neighborhood, it was clear their preparations would not be enough. As furious wind gusts approaching 100 miles per hour tore through the city and propelled showers of embers that ignited entire neighborhoods, Anthony Marrone, the chief of the Los Angeles County Fire Department, stood at a command post on the edge of the Pacific Ocean. Blasted by dust and dirt kicked up by the relentless wind, he snapped a picture with his phone of smoke obscuring the sun and looked out at a panorama of flames, smoke and debris. The fire, he thought to himself, looked unstoppable. It was moving “like a funnel, like a speedway,” he said. “I knew that if we had one start, we probably weren’t going to be able to contain it.” The conflagrations that killed at least 11 people and destroyed thousands of homes have raised questions about whether the dozens of federal, state, county and city fire departments involved in this week’s fire response deployed enough resources — and the extent to which modern firefighting tools are effective against the megafires that have become increasingly common in California over the past decade. It was only hours before a situation that bore no resemblance to an ordinary red-flag alert, the kind set off when the Santa Ana winds blow in over the Mojave Desert from the inland West, began to evolve. A second huge fire broke out in Altadena, the unincorporated area adjacent to Pasadena, destroying more than 5,000 structures. A third ignited in Sylmar, to the north, and yet another, the next day, in the Hollywood Hills.Chief Marrone quickly acknowledged that the 9,000 firefighters in the region were not enough to stay ahead of the fires.“We’re doing the very best we can, but no, we don’t have enough fire personnel,” he said at a news briefing on Wednesday afternoon. “The L.A. County Fire Department was prepared for one or two major brush fires, but not four.”The hurricane-force winds, low humidity and parched landscape created unusually perilous conditions: On the first day, when the Palisades and Eaton fires broke out, it was too windy by late afternoon to send up the aircraft whose drops of water and fire retardant might have helped slow the spread of the blazes. Chief Marrone said the parched terrain and the concentration of homes, surrounded by forested hillsides, also combined to create an indefensible landscape. “The next time I’m not going to do anything differently because I don’t feel that I did anything wrong this time,” he said in an interview.Los Angeles city fire officials had a similar view. “The fire chief did everything she could with the resources she had,” Patrick Leonard, a battalion chief with the Los Angeles Fire Department, said, referring to the city’s fire chief, Kristin Crowley. The question of resources will almost certainly arise in the weeks ahead as the fire response is analyzed. The Los Angeles Fire Department has said for years it is dangerously underfunded. A memo sent to city leaders in December by Chief Crowley complained that recent budget cuts had “severely limited the department’s capacity to prepare for, train for, and respond to large-scale emergencies, including wildfires.” But there are a host of other factors at play. Fire experts have long warned that climate change and more home-building outside of urban areas are straining firefighters’ ability to prevent and contain fires. As fires have grown in size and complexity, California has explored mitigation through thinning brush out of forests, safer power grids and shoring up home protection. But it has been far from enough, they say. The fires in Los Angeles have also raised the critical question of how departments can battle so many powerful infernos at once. After the Woolsey fire burned more than 1,600 structures in the northern part of the county in 2018 — at the same time that other major fires were raging across the state — Los Angeles County commissioned an assessment that found that the simultaneous outbreaks had slowed the ability of other fire agencies to fight the blaze because they were already busy. Lori Moore-Merrell, the head of the U.S. Fire Administration, a division of the Federal Emergency Management Agency, who flew this week to Los Angeles to inspect the firefighting efforts and damage, said she believed that the reason for the widespread devastation was not the firefighting response.“They deployed enough,” Dr. Moore-Merrell said in an interview. “This fire was so intense. There isn’t a fire department in the world that could have gotten in front of this.” The question of predeployment will almost certainly prove one of the keys to understanding the response. It nearly always involves weighing a host of unknown factors. Firefighting experts agree that having engines and firefighters very close to the site of an outbreak is essential, especially in very windy conditions; fires in those cases must be stamped out immediately, or they will very likely begin to spread out of control. “Once a wind-driven fire is well established you’re not going to put it out,” said Patrick Butler, a former assistant chief of the Los Angeles Fire Department who ran the response to many of the major fires the city has faced over the past decade. With the threat of highly destructive fires increasing, he said, fire authorities should “flood” fire-prone areas with extra fire engines and crews during times of high winds.But such predeployments are enormously costly, and fire chiefs often have a tough task convincing political leaders to repeatedly spend the money on them — especially when no fires break out. Chief Butler, who now runs the fire department in Redondo Beach, Calif., said he prepositioned firefighters on a large scale at least 30 times during heightened fire threats. Fires broke out after those threats just three times, but to him, it was worth the cost. “I’m not in the business of making decisions that are politically palatable,” he said.Chief Marrone began preparing for his own predeployments after meteorologists at the National Weather Service, on the first weekend of the new year, issued a bulletin warning of a “Particularly Dangerous Situation” — code words for a severe weather warning, the kind the federal government issues only about two dozen times a year. Based on the conditions in Los Angeles, it was clear that fire would almost certainly ensue. The chief authorized overtime and supplemental state funding to add 100 people for duty drawn from a pool of around 2,000 off-duty firefighters so they could have more units prepositioned in areas known to be vulnerable to fire, including Santa Clarita and the Santa Monica mountains. He prepositioned four strike teams, each with five trucks, and asked the California Department of Forestry and Fire Protection, the state fire agency known as Cal Fire, to preposition two more teams. The staffing was typical for a red-flag wind event, he said. Early on Tuesday morning, the chief ordered that 900 firefighters who were finishing their shifts stay on the job. The decision increased the number of county firefighters on duty to 1,800. And the U.S. Forest Service, which fights fires in national forests, also began mobilizing. Adrienne Freeman, an agency spokeswoman, said that on Monday, the day before the winds kicked up and the first fires started, the agency had 30 trucks from out of state and Northern California in place at four Southern California forests and at a local coordination center. On Monday night, the agency called in 50 more trucks that arrived on Tuesday, she said. The city fire department proceeded with prepositioning the nine fire trucks it was deploying on Tuesday morning, according to an internal document reviewed by The New York Times, three each in Hollywood, Sunland Valley — in the northwestern part of the city — and near the city of Calabasas in the western foothills. The extra 90 firefighters the city was predeploying were called up on overtime. No extra trucks were sent to Pacific Palisades. Those extra firefighters the city of Los Angeles called on made up less than a tenth of the approximately 1,000 on duty on any given day. And the 100 additional people called up by the county added to its daily firefighting force of 900.Mr. Leonard, the city battalion chief, said the trucks were positioned based on historical patterns of fire during high-wind events. “Predicting where the fire is going to start is a scientific guess,” he said. Then the wind started, and the first embers started flying. Chief Crowley, with the city department, texted the chiefs in the counties surrounding Los Angeles at 10:35 a.m. Tuesday, five minutes after the Palisades fire was first reported, notifying them, according to an account of the messages shared with The Times. Chief Marrone responded immediately. “What do you need?” he texted. The Ventura County chief said he was sending strike teams. “They’re on the road now,” he wrote. Orange County’s chief said he could provide three strike teams of five trucks each, along with a helicopter and a crew that uses hand tools to cut firebreaks. The Los Angeles Fire Department put out a call for off-duty members to come to their stations and scoured mechanic yards for vehicles. Tens of thousands of people were being evacuated out of Pacific Palisades as the fire spread out of the foothills, leaping across the four lanes of Pacific Coast Highway and wiping out restaurants and homes along the coast. Then, at 6:18 p.m. on Tuesday, came more stunning news: the second major fire, in Altadena, had ignited. Chief Marrone put Eaton Canyon, the site of the new fire, into a navigation app and set off from the Palisades. Stuck in bumper-to-bumper freeway traffic, he could see the fresh fire and its smoke swelling into the sky. Around 9 p.m., he called Brian Marshall, the chief of fire and rescue for the California Office of Emergency Services. Advertisement SKIP ADVERTISEMENT “I said, ‘We are out of resources, we need help,’” Chief Marrone said. He requested 50 strike teams, a total of 250 fire engines and 1,000 firefighters. At 10:29 p.m., a third major fire ignited in Sylmar, in the northernmost part of the San Fernando Valley, about 25 miles northwest of downtown Los Angeles, and a fourth broke out near Santa Clarita on Wednesday afternoon. Mutual aid teams from across the West, and beyond, began streaming toward Los Angeles. Firefighters tried and failed to stay ahead of the furious flames. “Resources were scarce” during the initial hours of the blazes, said Capt. Jason Rolston of the Orange County Fire Authority, who was among those who traveled to join the firefighting effort in Los Angeles. “There were too many houses to protect, and not enough fire engines.” The wind was gusting so powerfully that smoke boiled across the terrain. Firefighters said the barrage of ash and soot was so overwhelming at times that they struggled to even move through the fire zone. Advertisement SKIP ADVERTISEMENT “There would be times when you couldn’t see 10 feet in front of the rig,” said Capt. Shawn Stacy, another Orange County firefighter who deployed to the Palisades fire. “What went wrong is that you had 80-m.p.h. winds.”Some firefighters said there was so much demand on water systems that they ran out of water. Capt. Ryan Brumback of the Los Angeles County Fire Department said he was five hours into an all-out effort to save buildings in Altadena from the Eaton fire early Wednesday morning when the hydrants started running dry — a situation firefighters also faced in the Palisades. Suddenly, he said, “we noticed our hoses became very limp and soft.” The problem, he said, was that a power shut-off intended to prevent additional ignitions also shut off the pumps that help with water pressure in Altadena. “It was devastating, because you want to do all that you can do.” Advertisement SKIP ADVERTISEMENT By Friday, both initial major fires were still burning with little containment, and others that ignited later in the week also required aggressive responses, particularly in the Hollywood Hills on Wednesday evening and in the West Hills, northwest of Los Angeles, late on Thursday. Fire officials were still focused on saving lives and homes, and said they would spend time later looking at whether their preparations had been sufficient. “It wasn’t for a lack of preparation and decision making that resulted in this catastrophe,” Chief Marrone said at a news briefing on Saturday. “It was a natural disaster.” The coming analysis, several experts said, will have to take into account that the standard guidelines that have long determined red-alert fire responses may no longer apply, as weather and fires become more virulent. “There’s going to be a real reckoning about land use, escape routes, water pressure, water supply,” said Zev Yaroslavsky, a former longtime Los Angeles City Council member and county supervisor. Mr. Yaroslavsky said the fire might serve as a “Pearl Harbor” moment for the city, an alarm bell that signals fundamental new questions about how the city approaches the threat of wildfires. “A lot,” he said, “will be reassessed.”

A heavy mix of snow and sleet that swept across parts of the South is expected to melt and then freeze, making for slippery road conditions through Sunday, officials said. The storm on Friday struck areas unaccustomed to such winter weather, prompting flight cancellations, school closures and official warnings to stay off the roads when possible. A winter storm warning that stretched from eastern Oklahoma to Virginia was discontinued by Saturday morning, the National Weather Service said, after a mix of snow and freezing rain fell in cities including Jackson, Miss.; Birmingham, Ala.; and Atlanta. Advertisement SKIP ADVERTISEMENT On Saturday morning, areas in the Mid-Atlantic, parts of Virginia and southeastern Pennsylvania had received up to two inches of snow, according to the National Weather Service. Parts of Ohio and western Pennsylvania received up to five inches.Areas across the South, including southeastern Oklahoma and west-central Arkansas, will “have temperatures that are going to be in the 20s Sunday morning,” said Bob Oravec, a forecaster at the service. “A lot of melting is going to go on during the day, and then, as you might expect, freezing again at night,” he said. The widespread mix of wintry precipitation led to the cancellation of more than 3,000 flights in and out of airports in Atlanta, Dallas, Nashville and Charlotte, N.C., on Friday. That number had decreased to several hundred by Saturday morning. A ground stop was issued for Boston’s Logan Airport on Saturday morning, according to the Federal Aviation Administration, and multiple airports, including Dallas Fort Worth International and Cleveland Hopkins International, were undergoing de-icing procedures. At Atlanta’s Hartsfield-Jackson International Airport, where nearly 60 percent of outgoing flights had been canceled or delayed, a ground stop was issued for all incoming Delta flights on Friday after an aborted takeoff led to passengers on a Delta plane being evacuated onto the snowy runway, according to the F.A.A. A Delta spokeswoman said that four people were treated for minor injuries and that there was “no indication of weather being the cause of the engine issue.”On Saturday morning, more than 300 flights in and out of the airport were canceled. On social media, the airport asked passengers to be prepared for possible delays. The icy, snowy mix made streets and highways treacherous across a wide swath of the South. A section of Interstate 22 in Mississippi and Alabama was shut because of a crash in Marshall County, in north-central Mississippi. In northern Alabama, many roads were ice covered and impassable, Jim Stefkovich, a meteorologist with the state’s Emergency Management Agency, said in a statement. “If you’re trying to get on the roads, don’t get on them,” Gov. Brian P. Kemp of Georgia said at a news conference on Friday, warning that, with temperatures remaining near the freezing mark, the mix of snow and icy rain would likely make roads hazardous through Sunday. In Atlanta, most shops and restaurants were shuttered. The city seemed to have learned its lesson after less than three inches of snow led to chaos in 2014, leaving motorists stranded, children stuck in buses and schools and government leaders scrambling to clean up the mess. The city and state seemed better prepared this time. Officials urged people to stay indoors, and highways and city streets were salted before the storm. The roads were virtually empty on Friday — save the occasional skier or sledder — as the morning’s powder melted into slush around noon.One exception to the closures was Waffle House. Benji Waugh, a customer, knew the famously resilient breakfast joint would be open for business. “Living in the South, anytime there’s a hurricane or a tornado or some kind of storm, everywhere shuts down,” he said in an interview at the Waffle House across from Centennial Olympic Park in downtown Atlanta. “But it’s just easy to go to Waffle House, because they’re always open.” Governor Kemp declared a state of emergency on Thursday in anticipation of the storm, as did his counterparts in Tennessee and Arkansas. More than seven inches of snow was reported on Saturday morning at Memphis International Airport, according to the Weather Service.