At least 10 people, including a child, were dead after a severe rainstorm pounded a large section of the South and left hundreds of thousands of people without power on Sunday morning and communities contending with flash flooding. In Tennessee, the National Weather Service in Memphis issued a flash flood emergency on Sunday afternoon after a levee along the community of Rives failed, causing “rapid onset flooding” there and in the surrounding areas. “Get to high ground now,’’ the Weather Service warned on social media. Rives, which is northeast of Memphis, has a population about 300. The Tipton County Fire Department said that about 200 people needed to be rescued. Steve Carr, the Obion County mayor, declared a state of emergency on Sunday in response to the severe flooding. He said on Facebook that there would be mandatory evacuations in Rives because of “the rising water, no electricity, and freezing temperature creating a life-threatening situation.” Advertisement SKIP ADVERTISEMENT Some evacuees were taken to the hospital, according to the Obion County Emergency Management Agency. Mr. Carr added that other low-lying areas, including the town of Kenton about 13 miles south of Rives, also faced “imminent threats” because of the flooding. The Rives fire chief, Campbell Rice, pleaded on a Facebook livestream for residents to evacuate immediately. He said he had responded to floods every year for the past 35 years, but “this one is totally different from the ones in the past.” The levee was designed to hold back the Obion River, a major tributary of the Mississippi River. It was not immediately clear who was responsible for maintaining the levee. Kentucky was hit particularly hard by the rain and at least nine people died there because of the storms, Gov. Andy Beshear said on Sunday. He said at a news conference in the afternoon that officials expected the death toll to rise. Governor Beshear said there had been more than 1,000 rescues and there were more than 300 road closures. The governor said weather conditions were still dangerous in the state. And a snowstorm was expected to bring several inches of snow on Tuesday night. In Kentucky, a woman and her 7-year-old child died after the mother’s vehicle was swept away during flash flooding in Hart County, said Anthony Roberts, the county’s coroner. Donald K. Nicholson, 72, of Manchester, Ky., died when he was driving on Kentucky Route 80, said Jason Abner, the Clay County coroner. Mr. Nicholson got out of his vehicle when the road became impassable and was swept several hundred feet, Mr. Abner said. Advertisement SKIP ADVERTISEMENT Mr. Beshear said three other people also died in floodwaters and two people died in motor vehicle accidents. He confirmed another weather-related death in Pike County on Sunday evening. In Georgia, a person was killed in Atlanta after an “extremely large tree,” fell on a house during a thunderstorm early on Sunday, Capt. Scott Powell of the Atlanta Fire Rescue Department told reporters.In Virginia, there were over 150 water rescues and evacuations on Sunday, according to a news release from the governor’s office. The James River and other waterways reached their highest levels since 1977, according to the release. The weather system spawned at least two tornadoes over the weekend, one in Alabama on Saturday, four in Mississippi on Saturday evening and another in Tennessee on Sunday, according to the Weather Service. Advertisement SKIP ADVERTISEMENT L.D. Mosley, a 70-year-old retired coal company electrician, had just finished fixing his shed when a wall of mud, rocks and trees slammed into it on Saturday. The landslide came off the mountain behind his home in Hindman, Ky., which is about 130 miles southeast of Lexington. Mr. Mosley estimated that as much as 80 tons of earth covered his property. “I’m just so heartsick of it right now, I’d like to just throw my hands up and leave,” Mr. Mosley said. In the nearby community of Krypton, Ky., Scott McReynolds had lost power at his home and was stuck inside because of the water at the end of his driveway. Mr. McReynolds, the executive director of a housing nonprofit called the Housing Development Alliance, is involved in a statewide effort to move vulnerable residents out of floodplains and onto former strip mines that provide flat land for building new neighborhoods. He has lived in the region since 1992 and said that recent floods have been overwhelming. “The flood in 2021 was awful, and in 2022 it was unbelievable,” Mr. McReynolds said. “Now we’re doing it again.” In Hazard, a city about 14 miles southeast of Krypton, the Kentucky River had crested at 30.5 feet, the highest since 1984. Hazard’s downtown coordinator, Bailey Richards, said more than 40 businesses had flooded since the rain began on Saturday, including a diner and the fire and police departments. “It got so much higher than expected,” Ms. Richards said. “Most of the areas I didn’t consider could possibly flood ended up flooding.”

The Federal Emergency Management Agency has decided to stop enforcing rules designed to prevent flood damage to schools, libraries, fire stations and other public buildings. Experts say the move, which has not been publicly announced, could endanger public safety and may be in violation of federal law. The change in policy was laid out in a Feb. 4 memo by FEMA’s chief counsel, Adrian Sevier, that was viewed by The New York Times. The rule in question, called the Federal Flood Risk Management Standard, was one of the Biden administration’s most significant efforts to address the growing costs of disasters. The rule says that when public buildings in a flood zone are damaged or destroyed, those structures must be rebuilt in a way that prevents future flood damage if they are to qualify for FEMA funding. That could include elevating a structure above the expected height of a future flood or relocating it to a safer spot. In some cases, the standards also apply to private homes repaired or rebuilt in a flood plain. The rule has a tortured history. FEMA first proposed it in 2016, in response to an executive order from President Barack Obama. The powerful home-building industry opposed the rule on the grounds that it would increase construction costs. When President Trump first took office in 2017, he revoked Mr. Obama’s order, stopping FEMA’s effort. Soon after taking office in 2021, President Joseph R. Biden Jr. signed a new executive order calling for a federal flood standard, which culminated in a final rule issued by FEMA last July. The goal wasn’t just to protect people and property, according to Deanne Criswell, the head of FEMA at the time. It was also to save taxpayers’ money as climate change made flooding more frequent, causing buildings in flood plains to be repeatedly damaged and then repeatedly rebuilt with government help. “We are going to be able to put a stop to the cycle of response and recovery, and rinse and repeat,” Ms. Criswell said at the time. Mr. Trump, on his first day back in the White House, again revoked the executive order calling for a federal flood standard. In his memo last week, Mr. Sevier said that while FEMA considers how to amend the rule, the agency will not enforce it. “This pause must be implemented immediately while FEMA takes action to rescind or amend the policies,” Mr. Sevier wrote. In a statement, FEMA said that the flood rule “is under review per the president’s executive order.” But FEMA cannot simply stop enforcing a regulation, according to David A. Super, a visiting law professor at Yale University who specializes in administrative law. If the agency wants to reverse course, it must follow a process clearly laid out by federal law: issuing a public notice, seeking and reviewing public comments and then publishing a new final rule.

Before joining The New York Times last year, I had never covered a wildfire. I knew a lot, though, about a different kind of disaster: hurricanes. My first full-time reporting job was at The Sun Herald in Biloxi, Miss. I started in 2020, during one of the most active hurricane seasons on record. As the storms approached, I stood in the rain to talk to people filling sandbags. After the worst was over, I wore galoshes to interview residents desperately draining floodwaters from their houses. When driving into an area just hit by a hurricane, there are indications of what lies ahead before you see the devastation: downed trees and power lines, water pooling where it shouldn’t, warped fast-food signs. That’s why, driving into Altadena for the first time last month, I expected some kind of warning before I reached the total destruction wrought by the Eaton fire. Advertisement SKIP ADVERTISEMENT Instead, I looked left to make a turn and suddenly saw black, twisted ruins where a house should have been. Next door and across the street were homes that looked perfectly untouched. Hurricane-force winds had propelled embers at random, sparking house fires that firefighters couldn’t stop. The result was a jarring contrast that only heightened the sense of upheaval. This had been no hurricane. A hurricane may gather strength rapidly or change direction just before landfall, but it typically arrives with days of warning. It follows a path and often weakens with time. The Eaton fire seemed to follow its own windblown path, but it grew faster than many people could prepare for, and then lingered for weeks afterward. Hurricanes are slow, colossal beasts. Wildfires can be colossal beasts, too, but fast and mean. Hurricanes overwhelm structures but often leave them behind; fires consume them. Hurricanes smelled different, too. After Hurricane Helene in the Tampa area last year, I visited families cleaning mud from their homes and laying out photographs to dry in the sun. The air smelled like salt, sewage and traces of mildew. In Altadena, two weeks after the fire, the faint smell of smoke still lingered over the ash and dust. As I spoke with Altadena residents picking through the rubble of their lives, I thought about Trey Camardelle. The house where Mr. Camardelle’s parents lived was destroyed in Hurricane Zeta in 2020. The storm was nowhere near as destructive as the Eaton fire, but it damaged roofs, downed power lines and knocked his parents’ house right off its 18-foot cinder block pilings.The day after the storm hit, Mississippi’s governor met with Mr. Camardelle, and then began a news conference. While the governor spoke to a gathering of reporters, Mr. Camardelle was in the distance, walking around the jumble of wood and insulation, the battered house sitting off-kilter on top. This, he told me, was an “entire life, just gone.” In Altadena, the disaster was different, but the loss was much the same.

A powerful tropical cyclone was barreling toward the Pilbara region in northwestern Australia on Friday morning and was expected to bring destructive winds and flooding to a remote region that is home to ports and mines that are crucial to the global economy. It was about 60 miles offshore and was expected to make landfall in the afternoon, the authorities said. Tropical Cyclone Zelia had sustained wind speeds at its center of about 127 miles per hour with wind gusts of up to 177 miles per hour, according to Australia’s Bureau of Meteorology. This would make the storm equivalent to a Category 4 Atlantic hurricane. On Australia’s tropical cyclone scale, it falls within the highest classification level. “It doesn’t get worse than that. That is the most powerful tropical cyclone you can get,” Angus Hines, a senior meteorologist at the bureau, said in a briefing on Thursday. Advertisement SKIP ADVERTISEMENT While the Pilbara region, a desert, is sparsely populated, it is Australia’s mining heartland and home to major iron ore mines operated by Rio Tinto, Fortescue and BHP. A key port in the region has already closed. The storm may bring wind gusts of as much as 180 m.p.h. when it makes landfall, Mr. Hines said. That’s strong enough to destroy houses and “cause widespread damage and destruction,” he said. Zelia is also expected to bring flash flooding and coastal surges to the region, with some parts expected to receive more than 19.7 inches of rain. The storm has forced ports in the region to halt operations. Port Hedland, one of the largest iron ore ports in the world, closed on Wednesday, according to Pilbara Ports. Dampier Port, which is used by Rio Tinto, and the Port of Varanus Island, which is used as a processing hub for oil and other fuel, would close on Thursday afternoon, Pilbara Ports said. Rio Tinto said in a statement on Thursday that it had paused its Dampier Salt operation at Port Hedland and Dampier, and had cleared ships and trains from its ports in the region. The storm is expected to make landfall between the towns of Karratha, home to about 22,000 people, and Port Hedland, which has nearly 16,000 residents. Major roads in the region have been closed since Thursday, as were stores, national parks and a dozen schools.

California is about to get soaked, whipped and dumped on again. A robust storm system will sweep in from Wednesday night into Friday, bringing the threat of strong winds, heavy rain or snow to every part of the state. Officials are especially worried about the risk of flash flooding and mudslides in areas that were recently burned by wildfires in coastal Southern California. But across the entire state, power outages and airport delays as well as road closures from flooding, snow and downed trees are possible as the storm moves through. This system is also churning up the Pacific Ocean and will bring dangerous surf to beaches. Key things to know The heaviest rain and snow are expected Thursday. Some moisture brought modest amounts of rain to the San Francisco Bay Area and Central California overnight and to Southern California on Wednesday morning, but the main event starts Wednesday night and is expected to last until Friday afternoon. In Southern California, this storm is expected to be the strongest of the winter so far, raising the risk of flooding on roadways and streams and especially in wildfire burn scars. Daniel Swain, a climate scientist at the University of California, Los Angeles, said on Tuesday that he was especially concerned bursts of torrential rain over the burn scars left by the Palisades and Eaton fires in the Los Angeles area could trigger rivers of water, mud and debris. Some evacuation warnings have already been issued. In Northern California, rain is expected to be heaviest around the Bay Area and just south of it. Downtown San Francisco is likely to see at least see an inch of rain, and up to about three inches, which could lead to some nuisance flooding. This storm is on track to be the biggest snow producer so far this winter, with multiple feet of snow expected in the Sierra Nevada. Rain will bring a flash-flooding risk to Southern California. The storm is expected to be the strongest of the season so far for Southern California, which has seen an otherwise dry start to winter, even with the recent rains. The rain is on track to start out light on Wednesday night into Thursday morning, and pick up Thursday afternoon, before ending early Friday. Heavy rain could lead to flooding of roads, small creeks and streams along the coast, but the the biggest danger is the potential flow of debris from areas burned by wildfires, which could be life-threatening. Santa Barbara County issued an evacuation warning for people around an area that was burned by the Lake fire last year. Urban flooding is likely, especially in Santa Barbara and San Luis Obispo Counties, but Ryan Kittell, a National Weather Service meteorologist, said it was not expected to be as severe as it was in 2023 when, after storms, the streets of downtown Santa Barbara turned into rivers. “The totals don’t look as high for Santa Barbara as those storms, and the rainfall leading up to those storms is much less for this storm,” Mr. Kittell said. “But with that in mind, we do anticipate lots of road issues in Santa Barbara.” While the rainfall totals will add up across 48 hours, the short, sharp bursts of rain are the main threat. These could cause flash flooding that leads to flows of water, mud, boulders, trees and the ashen remains of debris in areas scorched by wildfires. There’s a 10 to 20 percent chance of thunderstorms in Los Angeles County, and these could bring the heavy rainfall rates that might cause a debris flow. But the heavy localized torrential downpours are possible even without thunderstorms as the most intense periods of the storm, whether that occurs across 15 or 60 minutes, “could be very heavy indeed,” Mr Swain said. The Weather Service said the concern for flash flooding was highest in areas burned by the Palisades and Eaton fires in January and by the Bridge fire in September. The southern half of the state will also get whipped by winds Wednesday through Friday, and the Weather Service warned that delays are possible at airports including Los Angeles International Airport. Northern California gets yet another round of rain. The northern part of the state has received more rain than normal this winter, and it’s about to get more. While this is not the biggest storm of the season for the area, one to three inches of rain is expected at the coast and in the valleys, and more is likely in the higher terrains. While there’s a risk of flooded roadways and streams from the coast across the Central Valley and into the Sierra foothills, the risk is expected to be lower than it was in the last storm that led the Russian River to spill over its banks. Winter storms more commonly deliver the heaviest precipitation to the northernmost parts of the region. This system, however, will be focused to the south — around San Francisco and into the Santa Cruz Mountains, Monterey and Big Sur. While a flood watch was issued for most parts of the Bay Area, “our biggest concern is flooding and landslides in Santa Cruz and Monterey Counties and some areas of the South Bay,” said Crystal Oudit, a meteorologist with the Weather Service in Monterey. The Sierra Nevada is expected to get a barrage of snow. The storm is on track to bring the biggest snow dump of the winter so far to the Sierra Nevada. Unlike the systems this winter that have delivered a mix of rain and snow, this one is expected to pile up multiple feet of snow. Three to five feet of snow is expected on Donner Pass, one of the most highly traveled passes in the state and a gateway into the Tahoe Basin. Andrew Schwartz, the lead scientist at the University of California, Berkeley, Central Sierra Snow Lab, said the storm would also bring impressive totals to the central and southern portion of the Sierra Nevada that have seen less snowfall than the northern half this winter. “I’m not sure if this will totally get us up to average in those areas, but it should help at least equalize things a little bit,” he said. The northern edge of the storm will brush Oregon and Washington, bringing lower precipitation amounts than in California and delivering a mix of rain, freezing rain and snow.

A winter storm is expected to bring much-needed rain and snow to Central and Southern California this week, but also a risk of flash flooding and mudslides, especially in San Luis Obispo and Santa Barbara Counties and areas of Los Angeles County that were burned by wildfires last month. The robust storm system will swing waves of moisture up and down the California coast, including the already saturated northern part of the state, while also sending moisture inland, adding feet of snow to the Sierra. The storm will pull in moisture from the subtropics, and the severity of its impacts will depend on where “the bulk of that moisture goes through and how slowly the storm moves,” said Kristan Lund, a meteorologist with the National Weather Service. Advertisement SKIP ADVERTISEMENT “We’re looking at likely seeing the strongest storm of the season and at least so far,” Ms. Lund said.It’s too early to pin down the forecast with certainty, but as of Monday, the most likely scenario is that rain ahead of the storm will arrive Tuesday night, with rainfall amounts anticipated to be light. After a brief lull of largely dry conditions from Wednesday afternoon, the storm is expected to arrive in San Luis Obispo and Santa Barbara Counties through the early hours of Thursday morning and then head to Ventura and Los Angeles Counties by late morning. However, behind the storm a cold front will sweep in, bringing intense rainfall that could set off life-threatening debris flows around recent burn areas, particularly in the areas of the Eaton, Palisades, Franklin and Bridge fires, said Andrew Rorke, a meteorologist with the National Weather Service in Los Angeles. “This will be the worrisome portion of the storm, as rainfall rates near one inch per hour will be possible,” Mr. Rorke said. The most intense period is expected between 4 p.m. Thursday and 4 a.m. Friday: The cold front, the storm’s final surge, moves into San Luis Obispo County late afternoon Thursday, and then pushes through to Santa Barbara, Ventura and Los Angeles Counties into Friday morning before exiting. The Weather Service issued a flash flood watch for all recent burn scars of southwest California, in effect from early Thursday afternoon through to Friday morning. Additional areas may be added. Expected rainfall totals will range from one to three inches at lower elevations, and three to six inches across mountains and foothills. Portions of San Luis Obispo county may receive almost twice these totals, with three to five inches around coasts, and six to 10 inches near the Santa Lucia mountains. Currently, portions of Southern California face a moderate risk of excessive rainfall, embedded within a broader slight risk for much of the Central and Southern California coast. The projected rain totals for Santa Barbara County are close to the amount of rain that fell across the area in February 2023, when flooding rains turned streets into rivers. But the flooding this week should be less severe if the storm unfolds as expected. Two years ago, there was a lot of rain leading up to the heavy rain on Feb. 9 and soils were saturated, whereas this year, the winter has started off dry and the ground will be able to absorb more of the rain. Snow is also expected to fall in the mountains at elevations as low as 5,000 to 7,000 feet. The highest elevations may see several feet of snow. Advertisement SKIP ADVERTISEMENT Southern California has not received as much rain this winter as areas to the north. and it had unusually low precipitation in January. The region has recently received a few rounds of light to moderate rain, and that, combined with the upcoming storm, could significantly reduce the risk of wildfires. “Recent rains, especially considering next week, may be sufficient enough to switch to low fire season, but conversations do need to be had before we make that official declaration,” Ms. Lund said.

As President Trump issues rapid-fire executive orders intended to drastically reduce the federal work force and dismantle several agencies, many federal employees are left wondering what the future holds. At the National Oceanic and Atmospheric Administration, the federal agency with wide-ranging responsibilities that include disentangling whales from fishing nets off Alaska, gathering satellite data on wildfires in California and issuing tornado warnings in Kansas, one question of many that remain unanswered is: What will happen to the National Weather Service? Mr. Trump has not yet described his plans for NOAA, whose research is considered essential to the study of climate change, or for the Weather Service. But this week, staff members participating in Elon Musk’s efforts to downsize the government arrived at the agency, as they have at several others since Mr. Trump’s inauguration. Many of the Trump administration’s early actions have followed a blueprint set out by Project 2025, a policy blueprint created by the conservative Heritage Foundation. The 900-page document, published in 2023, envisioned a significantly pared down federal government, and it may offer clues to the fate of the Weather Service. But first, some history. It started with some shipwrecks. The first national meteorological service in the United States was established in response to tragedy. Across just two years, 1868 and 1869, more than 500 people were killed and more than 3,000 vessels sunk or damaged, many by storms, on the Great Lakes, according to “A Century of Weather Service,” a history of the agency by Patrick Hughes. By February 1870, President Ulysses S. Grant, pushed by calls for a storm warning system, formally established the country’s first meteorological service as part of the U.S. Army. This service was part of the Department of Agriculture and later moved to the Department of Commerce. In 1970, the National Weather Service was officially established when President Richard Nixon created NOAA, aimed at providing “better protection of life and property from natural hazards,” within Commerce. Since then, Congress has considered restructuring NOAA and its offices, which besides the Weather Service include the National Ocean Service; Office of Oceanic and Atmospheric Research; National Environmental Satellite, Data and Information Service; National Marine Fisheries Service; and the Office of Marine and Aviation Operations. Congress has also considered moving NOAA to another department or making it an independent agency. And for several decades, conservatives in the pursuit of free market goals have advocated increasing the role of the private sector in American weather forecasting. How a forecast works now Today, the Weather Service is a dispersed operation. Many of its more than 4,000 employees work from 122 forecast offices across the country, where they continuously monitor local conditions, issue multiple daily forecasts and release warnings ahead of dangerous weather. Its staff also operates some additional offices with a specialized remit, including one that is tasked with monitoring flooding, units that advise air traffic controllers, and the National Hurricane Center. By its own estimate, the Weather Service collects over six billion weather observations a day. To create a forecast, a meteorologist at a local office may analyze some of those data points, consult weather models and make judgments based on expertise. But the service’s mission goes beyond forecasting. In April 2011, after a large — and accurately predicted — tornado outbreak killed more than 300 people across the South, the department began providing advice to emergency agencies and public officials. It started telling people what to do with the information its forecasts were providing. Rob Dale, the deputy emergency manager for Ingham County, Mich., works closely with the Weather Service. “Michigan State University’s in our jurisdiction, and they send a meteorologist out to every football game here, just to monitor the lightning threat or severe weather threat,” Mr. Dale said. “There’s someone right in the room as we go through the decision-making process.” The Weather Service provides its forecasts and warnings to the public free of charge. NOAA’s observational data, from the agency’s vast network of satellites, buoys, weather balloons and sensors, is also available at no cost; companies like AccuWeather, Google and Apple use it to power their weather products. The Weather Service estimates that its services cost every American resident $4 per year. How the Weather Service could change The chapter of the Project 2025 document that includes proposals for NOAA describes the agency as a “colossal operation that has become one of the main drivers of the climate change alarm industry,” and calls for it to be “broken up and downsized.” It proposes that the Weather Service focus on its data-gathering services and “fully commercialize” its forecasting operations. Mr. Trump’s nominee for Commerce Secretary, Howard Lutnick, a billionaire Wall Street executive, told senators during his confirmation hearing in late January that he did not agree with Project 2025’s proposal to dismantle NOAA and eliminate many of its functions. He also said, during questioning from Senator Amy Klobuchar, Democrat of Minnesota, that he would maintain the Weather Service.But in the same exchange with Ms. Klobuchar, Mr. Lutnick also appeared to allow for the possibility that the private sector could take up the forecasts that have traditionally been Weather Service work. “I think we can deliver the product more efficiently and less expensively, dramatically less expensively,” he said, “but the outcome of delivering those services should not be changed.” The Weather Service during Mr. Trump’s first term Mr. Trump has shown a preference for the private sector when it comes to weather. During his first term, he nominated Barry Myers, the former chief executive of AccuWeather, one of the nation’s largest private weather forecasters, to lead NOAA. Mr. Myers remained unconfirmed by the Senate for more than two years. He withdrew from the process in 2019, criticizing Democrats who had voiced concerns over his possible conflicts of interest. (In a statement last year, AccuWeather appeared to distance itself from Project 2025’s proposal to fully privatize the weather system. “AccuWeather does not agree with the view, and AccuWeather has not suggested, that the National Weather Service (NWS) should fully commercialize its operations,” its chief executive, Steven R. Smith, said. The public-private partnership approach in forecasting “has saved countless lives,” he said.) Mr. Trump’s influence on the Weather Service was felt elsewhere during his first term. In a 2019 episode that came to be known as “Sharpiegate,” Mr. Trump was at odds with government meteorologists over the forecast for Hurricane Dorian. After he included Alabama on a list of states that he claimed would be hit by the storm, a Weather Service office in Birmingham clarified on social media that the hurricane would not affect the state. Days later, during a news briefing, Mr. Trump brandished an illustration of the storm’s path that had been altered with a thick black marker to include Alabama. Bowing to pressure, Neil Jacobs, then NOAA’s acting administrator, issued a statement that supported Mr. Trump’s assertions and criticized the Alabama forecasters for their post. An investigation found Dr. Jacobs had violated the agency’s policy for scientific integrity in issuing the statement. This week, Mr. Trump nominated Dr. Jacobs to the post of NOAA administrator again. The future of weather If confirmed, Dr. Jacobs would lead NOAA at a time when the balance of its public-private partnership may already be in flux. Studies show extreme weather events are becoming more frequent and more intense as a result of climate change. At the same time, weather models driven by artificial intelligence have demonstrated an ability to produce forecasts that are more accurate than traditional weather models. A crop of private companies that use A.I. to build their forecasts is leading the charge to adopt the technology more widely. Companies are now increasingly operating their own weather observation instruments, though many also still use NOAA data. In recent years, NOAA, too, has begun supplementing the data it collects with data purchased from the private sector. In Michigan, Mr. Dale worries that commercializing the Weather Service’s forecasting could set up a pay-to-play system for lifesaving warnings. “If someone says, ‘Hey, if you want a tornado warning for your county, you’re going to have to pay us, $100,000 a year,’ that’s just not viable,” he said. “There’s no spare money in most county budgets these days to do something like that.” Louis Uccellini, who was the Weather Service director between 2013 and 2022 and described himself as “one of the biggest supporters” of the private sector’s role in weather, said he believed not all the department’s work could be successfully contracted out. “Public service is not measured by the bottom line,” he said, “but by how well we serve society with the resources allocated by Congress.”

Two tornadoes touched down in eastern Tennessee on Thursday night, killing two people and causing widespread damage to rural communities outside Knoxville, the authorities said. In Morgan County, Tenn., a mother and daughter were killed at home and three other people were injured when a tornado touched down about 8 p.m., according to local emergency management officials. The tornado also damaged or destroyed more than a dozen homes, WVLT News reported. The National Weather Service in Morristown, Tenn., confirmed that the tornado, which was rated an EF2, reached wind speeds of up to 135 miles per hour. The second tornado, which hit Grainger County, Tenn., about 9:30 p.m., was rated an EF1 tornado with wind speeds of up to 110 m.p.h., according to the Weather Service. There were no deaths or reports of residential damage. Advertisement SKIP ADVERTISEMENT Researchers rate tornadoes using the Enhanced Fujita Scale (EF) from 0 to 5. Gov. Bill Lee of Tennessee said on social media that he would travel to the area on Friday and asked that his followers join him “in lifting our neighboring Tennesseans up in prayer as response teams help survivors.” Last year was among the most intense years for tornadoes in a decade, bringing 1,910 confirmed tornadoes across the United States. Twenty tornadoes have already been confirmed in 2025. The tornadoes in Morgan and Grainger Counties were the first in eastern Tennessee this year, the Weather Service said. Since 1950, the area has experienced 13 confirmed tornadoes in the month of February. The severe weather also affected power, phone and internet communications across the area. As of Friday morning, the Tennessee Emergency Management Agency said there were 2,300 reports of power outages statewide.In Morgan County, more than 100 emergency workers were deployed to canvass the area in the aftermath of the tornado. The storm also brought heavy rains, winds and hail, said Aaron Evans, a spokesman for emergency management in Morgan County. In an interview, Mr. Evans said that the community had grown accustomed to severe weather events, adding that the county had experienced three tornadoes in the past three years. “Unfortunately, everyone is kind of familiar with what goes on and what could happen,” Mr. Evans said. “Everyone tries to be well prepared.” Mr. Evans said his agency had received dozens of calls from residents offering help with food, water and other donated supplies, adding that the close-knit community is full of residents willing to help their fellow neighbors. “These are especially resilient people,” Mr. Evans said.

Last week, as forecasters at the National Weather Service in the San Francisco Bay Area looked at a series of storms that would hammer the region, they predicted that some areas in the North Bay would see six to eight inches of rain between Saturday and Tuesday. Instead, around a foot of rain fell at the wettest locations. Highways were flooded, landslides were triggered, and rivers swelled. By Tuesday afternoon, a house slid down a saturated hillside and fell into the Russian River in Sonoma County. Evening evacuation orders were issued, hours before the swollen river started spilling over onto a handful of roadways. The storms, known as atmospheric rivers, are a common feature of West Coast winters. They’re thin ribbons of moisture carried by powerful winds, sometimes for thousands of miles, which can make forecasting them especially challenging. “We got a little more rain than expected, and the rivers responded more than expected as well,” said Dylan Flynn, a meteorologist with the Weather Service. “A couple days ago we didn’t expect any of the rivers to flood.” The rain could have been even more impactful if Northern California hadn’t seen an abnormally dry January. The first of the recent rains was mostly absorbed by the dry soil starved of rain, sparing the area from more severe flooding. Another one of these moisture-rich storms is slated to sweep the region Thursday into Friday, bringing more rain and flooding concerns, but Mr. Flynn said this one is expected to be more “run-of-the-mill” than the last.This prolonged spell of atmospheric-river activity in Northern California has brought rain to the valleys and coast and snow to the mountains. The storms’ effects have stretched as far north as Washington and into Southern California. To pinpoint where these systems will land, meteorologists use tools far more sophisticated than what was available two decades ago, including higher-resolution satellites and weather models run on supercomputers. There’s even a program to fly hurricane-hunter planes from the National Oceanic and Atmospheric Administration into the storms to collect data. Still, it is tricky to predict these systems with perfect accuracy. A misforecast can result in surprises. Strong atmospheric rivers carry copious amounts of moisture, and if a storm unexpectedly shifts slightly one way or another, it can bring a lot of rain to one watershed versus another, consequently leading to one river to flood while another remains safely in its banks. Chad Hecht, a meteorologist with the Center for Western Weather and Water Extremes at the University of California, San Diego, said pockets of intense rainfall can occur within these storms and lead to hazards such as urban flooding or mudslides in areas where wildfires have recently burned. “These pockets can form at such small scales that forecast models struggle to resolve them, and it’s hard to identify exactly when and where they will occur,” Mr. Hecht said. As these storms began taking shape last week, there was some concern that they could shift south to Los Angeles, where devastating wildfires last month left the ground scarred. Instead, by early this week, forecasters said they expected only up to about an inch of rain for some parts of that region. And by Wednesday, they said, the storm was “underperforming” there, with up to half an inch of rain measured. Atmospheric rivers are corridors of moisture transported through the atmosphere by powerful winds. They’ve long existed all over the world, but the term was only first used in scientific literature in the 1990s, and the media quickly latched onto the colorful description.On the West Coast, the systems form over the Pacific Ocean in the subtropics. As they travel over the ocean, they pull in moisture and move across a vast, empty expanse where observational data is sparse compared with what the robust network of weather stations on land can collect. There are about 100 buoys managed by NOAA in the Pacific, the world’s largest ocean, that help predict the approach of a storm, versus 1,000 observational data points that can forecast the storm’s course once it reaches land, said Marty Ralph, the director of the Center for Western Weather and Water Extremes. “Satellites help, but big gaps remain,” Mr. Ralph said. Cliff Mass, a professor of atmospheric science at the University of Washington, said that today’s sophisticated satellites mostly make up for the lack of observational data available over the ocean. He’d like to see more high-powered, long-distance radar set up along the West Coast to collect data from the ocean as a storm approaches. “We can take the data from those radars and take it into our models, and then we could substantially improve our forecasts,” Mr. Mass said. Even with all the tools available, a forecast is a precarious undertaking, because while the storms can be thousands of miles long, they’re also narrow at only a few hundred miles across. “Because of that narrow plume of moisture, these system can literally thread the needle between observations,” said Brian Garcia, a meteorologist with the Weather Service. When these storms hit land, they’re wrung out like sponges. Forecasters are tasked with pinpointing where the systems will unleash that moisture. One thing they know for certain is that these systems are likely to release the most rain when they interact with mountains on West Coast, where there are a lot of large ranges, including the Siskiyous and the Sierra Nevada. “Because the mountains don’t move, especially relative to the weather, that makes it easier to predict where the heavy rain or snow is going to be,” Mr. Ralph said. While the mountains don’t move, the actual storms can make slight yet unpredictable shifts because of disturbances in the atmosphere. Mr. Garcia said that atmospheric rivers travel through the air more like a Frisbee with a wobble than like an arrow with a straight path. In the case of the system that swept California from Monday night into Tuesday, Mr. Garcia said it “wobbled” into the Bay Area, resulting in over a foot of rain on Mount Tamalpais in Marin County. Just across the Golden Gate Bridge, San Francisco recorded 2.8 inches of rain on Tuesday, breaking its same-day rainfall record of 2.2 inches set in 1882. The region is expected to get more rain on Thursday and Friday, though that storm is expected to be less impactful than the previous two. By the end of the day on Friday, Mr. Garcia said, some of the wettest locations in the North Bay may have recorded up to 18 inches of rain over the last week.

Even as much of the United States shivered under frigid conditions last month, the planet as a whole had its warmest January on record, scientists said on Thursday. The warmth came as something of a surprise to climate researchers. It occurred during La Niña conditions in the Pacific Ocean, which tend to lower the globe’s average temperature, at least temporarily. Earth’s surface has now been so warm for so much of the past two years that scientists are examining whether something else in the planet’s chemistry might have changed, something that is boosting temperatures beyond what carbon emissions alone can explain. Those emissions, the byproduct of burning coal, gas and oil, remain the main driver of global warming, which reached record levels in both 2023 and 2024. Advertisement SKIP ADVERTISEMENT It’s because of La Niña that scientists expected this year to be slightly cooler than the past two years, both of which experienced the opposite pattern, El Niño. The waters of the eastern tropical Pacific oscillate between El Niño and La Niña conditions, influencing weather worldwide by changing the balance between heat in the ocean and heat in the air. But a host of other factors figure into global temperatures as well. At the moment, chances aren’t high that 2025 will end up being the hottest year on the books, Russell Vose, a climate scientist at the National Oceanic and Atmospheric Administration, told reporters recently. But this time last year, researchers were saying much the same thing about 2024, Dr. Vose said. They were wrong.“So it’s a tough game, forecasting global temperature,” Dr. Vose said. According to Copernicus, the European Union climate monitoring agency, last month was much balmier than usual in northern Canada, Alaska and Siberia, as well as parts of Australia and Antarctica. Abnormally high temperatures above the Hudson Bay and the Labrador Sea helped shrink Arctic sea ice to a record low for January, Copernicus said. As scientists try to explain the unending streak of worldwide warmth, one thing they’ve focused on is reductions in air pollution. Advertisement SKIP ADVERTISEMENT In a report this week, James Hansen, the famed former NASA scientist, argued that cutting pollution had already played a big role in causing global warming to accelerate. The reason is a little counterintuitive: For decades, humans have not only been emitting carbon dioxide and other greenhouse gases when they burn fossil fuels. They’ve also been spewing tiny sulfate particles into the air. These particles spur the formation of more and brighter clouds, which help shield Earth from the sun. But as regulators have curbed sulfate pollution to protect people’s lungs, this cooling effect has diminished, exposing the planet to more of the full force of greenhouse warming. Three decades ago, Dr. Hansen was among the first scientists to draw broad attention to climate change. Speaking to reporters this week, he argued that the United Nations was ill-prepared to address accelerated warming. The U.N.’s approach to meeting its climate goals still counts on societies to slash their carbon emissions in the coming decades, he said. Those goals now look “impossible” to achieve, Dr. Hansen said, “unless some miracle occurs that we don’t understand.”