Schools shuttered early and cities warned of probable power outages, as potentially dangerous thunderstorms threatened the Upper Midwest late Monday afternoon. In northeast Iowa, southeast Minnesota and western Wisconsin, residents were bracing for storms that could bring high winds, tornadoes and hail the size of Ping-Pong balls. The Upper Midwest is accustomed to severe weather, but the high level of risk for very large hail and strong tornadoes caused alarm for state and local officials, who activated emergency operations centers and closed nonemergency city buildings. “We always have severe weather, I guess, in Iowa,” said Superintendent Joe Carter of the Algona Community School District, about two hours north of Des Moines. “I think the difference with this one is the threat of really, really strong stuff, such as tornadoes, and with a Category 4 ranking of severity.” A large area that includes Minneapolis and St. Paul is under a relatively high risk (Level 4 out of 5) for severe weather, according to the National Weather Service’s Storm Prediction Center. Advertisement SKIP ADVERTISEMENT At least five school districts across north central Iowa announced early closings on Monday afternoon. The Algona Community School District let out classes at 2 p.m. and canceled afterschool track and golf meets so that buses could get students home throughout the 400-square-mile district before storms descended by early evening. In the Twin Cities region of Minnesota, Minneapolis closed some city facilities early Monday afternoon and set in motion a team to try to persuade homeless people to take shelter before the storm arrived. In St. Paul, the school district preemptively canceled afterschool activities. Brennan Dettmann, a local meteorologist at the National Weather Service, said that it was unusual to see such a big storm at this time of year. “All of the hazards that can come with severe storms are on the table,” he said. “We’re expecting that if the line stays organized, you’re looking at more of a threat from wind and hail. But if it breaks into more scattered storms, the threat of tornadoes goes up.” He urged residents to have a plan in place to take shelter in case of an emergency. The Central and Southern Plains are also facing some risk on Monday, particularly across north-central Oklahoma, the Concho Valley and the Rolling Plains of West Texas. In these areas, recent heavy rains have already soaked the ground, increasing the likelihood of flash flooding. An area spread between the Northern Plains and the Upper Midwest may also be at some risk for heavy rains that could lead to flooding. The Quad Cities and the Twin Cities, along with Milwaukee and Madison, Wis., could see isolated flash flooding. Chad Hahn, a meteorologist with the National Weather Service in Des Moines, said on Monday afternoon that the agency was tracking thunderstorms developing across northwestern Iowa that had already produced baseball-size hail across the border in Minnesota. Forecasters expected the storms to continue east and grow, both in coverage and intensity, over the next several hours. “We expect the potential for very large hail, the potential for tornadoes, some that could be strong, and for damaging winds as they move through,” he said. “So definitely an active night that’s unfolding across the state of Iowa.” In Iowa, Mr. Carter, the school superintendent, said he planned to stay in the office until all buses returned to school property. “When I go home, like everyone, I’ll be making sure everything outside is secure,” he said. “And then it’s kind of a waiting game. We could very well be looking at a situation where we don’t have any severe weather, and that would be great and best for everyone. But we needed to prepare for the worst scenario.”

Much of the New York City region was under an air quality advisory on Thursday as smoke from one of New Jersey’s largest wildfires in two decades made its way north. The fire, which has been burning in Ocean County since Tuesday morning, has grown to 15,000 acres, mostly in the heavily forested Pine Barrens. Earlier this week, the fire forced officials to shut down the Garden State Parkway for miles and prompted the temporary evacuation of thousands of people in Ocean and Lacey Townships, the state’s Forest Fire Service said. A man has been charged with arson. Smoke from the fires spread over a large portion of New Jersey on Tuesday and Wednesday, prompting warnings about the air quality and at times irritating peoples’ eyes and making it difficult to breathe. By early Thursday, the smoke had spread to the north, prompting an air quality health advisory that was in effect through the end of the day for New York City as well as Nassau, Suffolk, Westchester and Rockland Counties. The New York State Department of Environmental Conservation warned that the air quality index, a measure of pollutants, was likely to climb above 100, which means the air is unhealthy for sensitive groups like very young people or those with asthma or other respiratory problems. At 5 a.m., the air quality index for the New York City region had reached 83, while Newark was at 80 and Philadelphia at 77, all within the moderate risk category. Nearby, Long Island was at 33, which is categorized as “good.” By early afternoon, the index as at 67 in New York, 72 in Newark and 76 in Philadelphia, while Long Island had inched up to 40. The air quality advisories were in effect through midnight. Southwesterly winds on Thursday afternoon were expected to spread the wildfire smoke toward Long Island. “New York and Long Island, especially Long Island and the boroughs in New York are most at risk today,” said Brian Hurley, a meteorologist with the Weather Prediction Center. “Also southern parts of upstate New York, south of Albany and southern Poughkeepsie, but it’s really confined to the metro region.” By Friday the smoke is expected to thin and clear, as stronger winds develop and rain spreads to the region later in the day. There have been no injuries and no homes were damaged as the fire has spread west through the mostly forested area of the Pine Barrens, part of a containment strategy meant to protect homes closer to the coast. On Wednesday, the authorities said they expected the fire to grow even as efforts to contain it gained ground. Fire authorities said the blaze may become one of the largest wildfires in the state since 2007, when a flare dropped by an F-16 fighter jet ignited a fire that ultimately consumed 17,000 acres. Much of the state was at elevated risk for wildfires this week, and by Wednesday the entire state was under a “high” rating, the middle point of a five-point scale that the state uses. Fuel like dry grass that would help any fire spread more easily has been especially dry, as the southern part of the state remains in drought conditions. Rain toward the end of the week is expected to give firefighters a helping hand in bringing the fire more under control. “There’s going to be slight chance of rain later Friday and into Saturday,” Mr. Hurley said. “Saturday is going to be the day with the best chance of rain. So that will definitely help.”

As an institution devoted to telling the story of the sea, the Mystic Seaport Museum has an inherently close relationship with water. Sitting along the Mystic River in southeastern Connecticut, its campus spans 19 acres and nearly 150 structures, including exhibition spaces and a re-creation of a 19th-century New England coastal town. Along the museum’s waterfront, it has an active seaport and a marina where roughly 900 boats dock annually. For nearly a century, the organization has maintained a harmonious relationship with the river. Flooding caused by storms, high tides and heavy winds occurred occasionally, but were not cause for great alarm. However, with storms becoming more severe and sea levels expected to rise substantially in the coming decades, the museum faces a daunting challenge: how to stave off the inevitable. Planning has begun to protect the museum’s history and properties, but the scope of the effort, as well as the costs, are immense. Nevertheless, the museum may have little choice. “Twenty years ago, there might have been an inundation a few times a year,” Chad Frost, principal of the landscape architecture firm Kent and Frost, which has been working with the museum for two decades, said in a video interview. “Now, we’re seeing degrees of flooding on a monthly, sometimes weekly, occurrence.” The museum’s location has made it especially vulnerable. It was constructed on the site of an 1830s shipyard built by three mariner brothers, George, Clark, and Thomas Greenman. They, like other entrepreneurs in the booming seafaring community of Mystic, took over low-lying and marshy lands whose gently sloping banks and proximity to the Atlantic Ocean were opportune for shipbuilding. When the museum was established in 1929 as the Marine Historical Association, a steady expansion began, with land filled in and bulkheads added along the river. “This kind of development was happening along the entire Connecticut coast around 100 to 80 years ago,” Frost said. “Now we know that fill settles over time. Add to that the fact that we didn’t have the foresight to know about climate change and rising sea levels — areas once habitable are being forced to adapt.” Today, the majority of the campus is in a FEMA-designated flood zone. Among the highest points — at just 14 feet above sea level — are the museum’s offices, which were originally the Greenman brothers’ homes. “It’s a testament to how forward-thinking these mariners were,” said Shannon McKenzie, the museum’s vice president of watercraft operations and preservation, in a video interview. “They knew the river would be a threat long before people were concerned about sea level rise.” Flooding often submerges walkways throughout the campus, preventing visitors from accessing buildings and experiences. Some structures, especially those along the waterfront like the Thomas Oyster House — which operated in the thriving oyster distribution hub of New Haven from 1874 to 1956 and was donated in 1970 and placed on its current site on a museum pier in 1984 — also become flooded.

Our universe might be chock-full of cosmic wonder, but you can observe only a fraction of astronomical phenomena with your naked eye. Meteor showers, natural fireworks that streak brightly across the night sky, are one of them. The latest observable meteor shower will be the Lyrids, which has been active since April 15 and is forecast to continue until April 30. The shower reaches its peak April 21 to 22, or Monday night into Tuesday morning. Best seen from the Northern Hemisphere, the Lyrids are caused by the dusty debris from a comet named Thatcher and spring from the constellation Lyra. During this year’s period of peak activity, viewers may have a more difficult time seeing meteors from this shower because the moon will be 40 percent full. States bordering the western bank of the Mississippi River may have good odds of glimpsing a few fireballs. But thick cloud cover is expected over all the states east of the river. Tuesday night, when the shower is still active but past its peak, looks slightly better for the eastern half of the U.S. Apart from high clouds in the Texas Panhandle and low clouds hugging the Gulf Coast, the Lone Star State may be one of the best places to see this evening. Cloud cover will create viewing obstacles above the Northern Plains, the Desert Southwest and also up through the central and northern Rocky Mountains. There is more hope out west, primarily in Northern California, Nevada and Utah. To get a hint at when to watch, you can use a meter that relies on data from the Global Meteor Network showing when real-time fireball activity levels increase in the coming days. Where meteor showers come from There is a chance you might see a meteor on any given night, but you are most likely to catch one during a shower. Meteor showers are caused by Earth passing through the rubble trailing a comet or asteroid as it swings around the sun. This debris, which can be as small as a grain of sand, leaves behind a glowing stream of light as it burns up in Earth’s atmosphere. Meteor showers occur around the same time every year and can last for days or weeks. But there is only a small window when each shower is at its peak, which happens when Earth reaches the densest part of the cosmic debris. The peak is the best time to look for a shower. From our point of view on Earth, the meteors will appear to come from the same point in the sky. The Perseid meteor shower, for example, peaks in mid-August from the constellation Perseus. The Geminids, which occur every December, radiate from the constellation Gemini. Bookmark the Times Space and Astronomy Calendar for reminders about meteor showers throughout the year. How to watch a meteor shower Michelle Nichols, the director of public observing at the Adler Planetarium in Chicago, recommends forgoing the use of telescopes or binoculars while watching a meteor shower. “You just need your eyes and, ideally, a dark sky,” she said. That’s because meteors can shoot across large swaths of the sky, so observing equipment can limit your field of view. Some showers are strong enough to produce up to 100 streaks an hour, according to the American Meteor Society, though you likely won’t see that many. “Almost everybody is under a light polluted sky,” Ms. Nichols said. “You may think you’re under a dark sky, but in reality, even in a small town, you can have bright lights nearby.” Planetariums, local astronomy clubs or even maps like this one can help you figure out where to get away from excessive light. The best conditions for catching a meteor shower are a clear sky with no moon or cloud cover, at sometime between midnight and sunrise. (Moonlight affects visibility in the same way as light pollution, washing out fainter sources of light in the sky.) Make sure to give your eyes at least 30 minutes to adjust to seeing in the dark. Ms. Nichols also recommends wearing layers, even during the summer. “You’re going to be sitting there for quite a while, watching,” she said. “It’s going to get chilly, even in August.” Bring a cup of cocoa or tea for even more warmth. Then lie back, scan the sky and enjoy the show.

Three people, including a 12-year-old boy, died after severe weather struck Oklahoma on Saturday as part of a sprawling storm system that was bringing damaging winds and the threat of tornadoes to the South and Midwest on Sunday. Wind gusts of up to 70 miles per hour and pea-size hail swept through parts of Arkansas, Illinois, Missouri and Oklahoma on Sunday, and thunderstorms were expected across south-central Texas, posing a risk for travelers on the Easter holiday weekend, according to the National Weather Service. In towns across Missouri and Arkansas, powerful winds damaged roofs and brought down power lines. Residents in those places spent Sunday afternoon under tornado watches and warnings, which persisted into the evening. On Saturday night, one person was killed and another was injured after a tornado touched down in Spaulding, Okla., according to Hughes County Emergency Management. Two homes were destroyed, county officials said. In Moore, Okla., which is about 11 miles south of Oklahoma City, a woman and a 12-year-old boy were found dead after a vehicle they were in became stranded in floodwaters. The vehicle was swept under a bridge, the Moore Police Department said. Rescue workers responded to the stranded vehicle around 9 p.m. on Saturday and were able to rescue all but two people who were inside. The authorities first declared the two people missing, but they were later found dead, the authorities said. “This was a historical weather event that impacted roads and resulted in dozens of high-water incidents across the city,” the Police Department said. The severe storms were expected to move across Missouri through Sunday night and could produce hail the size of golf balls, winds up to 70 miles per hour and strong tornadoes, according to the Weather Service. In Arkansas, storms were possible across much of the state, especially in the north. Large hail, damaging winds and tornadoes were possible into Sunday night. Editors’ Picks How Pickle Lemonade Took Over the Group Chat Kristen Stewart Thinks the Critics at Cannes Are Being Too Nice Living the Slop Life The Weather Service warned that flooding could occur in much of Oklahoma on Sunday, and flood warnings, which mean a flood is occurring or imminent, were in place across the state. Severe thunderstorms on Saturday led to at least one tornado in Texas and heavy rains, flooding and large hail in Arkansas, Missouri and Oklahoma. The storm system is moving at a slow pace, which may lead thunderstorms to repeatedly break out over the same regions, increasing the risk of flash flooding. Severe storms could continue in the area beyond the weekend, forecasters said. Heavy rains could lead to flash flooding through Monday morning. Precipitation levels are expected to remain above normal from the Midwest to the Mid-Atlantic through the end of April, according to the Weather Service’s Climate Prediction Center’s outlook. This is particularly true for Northeast Texas, North Louisiana, Arkansas, eastern Oklahoma and southern Missouri.

The National Weather Service is preparing for the probability that fewer forecast updates will be fine-tuned by specialists, among other cutbacks, because of “severe shortages” of meteorologists and other employees, according to an internal agency document. An agreement signed on April 10 between the service and the union representing its employees describes several measures that forecasting offices will take to manage the consequences of the Trump administration’s drive to reduce the size of the government. The document also says the service might reduce or suspend the launches of data-gathering weather balloons and eliminate the testing of new forecasting methods and technologies. More than 500 people this year have already left the National Oceanic and Atmospheric Administration, which oversees the National Weather Service. Nearly 200 of those departures were people who work in weather forecasting offices, which had already faced serious understaffing. About 300 additional people are expected to leave under the Trump administration’s latest resignation offer, according to two people familiar with the matter, who asked for anonymity because the administration has not officially made agency departure numbers public. Union officials said the departures at NOAA since President Trump took office have far exceeded the typical turnover rate. The agreement indicates that field offices across the country could face vacancy rates as high as 35 percent, compared with current staffing levels, according to the union. Parts of the agency had already been operating at lower-than-usual staffing levels well before the Trump administration’s cost-cutting efforts. The document outlines options for cutting back programs and allows the National Weather Service to offer “degraded” services as more meteorologists retire or resign. The cuts would significantly scale back the work of the 122 weather offices nationwide, which collect weather observations and issue warnings during severe weather events. Representative Zoe Lofgren, the senior Democrat on the House Committee on Science, Space and Technology, which oversees the Weather Service, said the Trump administration was endangering the agency’s lifesaving work. Democrats on the committee provided a copy of the document to The New York Times. “Chaotic and illegal firings, coercions to resign, reductions in force, and a general obsession with destroying the morale of dedicated public servants have left the National Weather Service’s work force so strained they cannot carry out their duties as they once did,” Ms. Lofgren said in a statement. Tom Fahy, the legislative counsel for the union, the National Weather Service Employees Organization, said the agreement had been developed to alleviate staff burnout. “In the last four months our losses are unprecedented, and our offices are struggling to maintain operations,” he said.

In the beach towns west of Tampa, Fla., the message was clear for any spring breaker passing through. It appeared on chalkboard signs, waving inflatables and posters: We are open. Spring break season is fraught in some parts of Florida, where the raucous behavior of certain visitors can outweigh their economic benefit. Miami Beach has been on a yearslong campaign to deter the college crowd, including with an ad this year for a fake reality show in which partyers break the rules and suffer consequences. But for the businesses and the restaurants along the Gulf of Mexico that were ravaged by Hurricanes Helene and Milton last year, welcoming spring breakers — and anyone else, really — has been imperative. Some are still in temporary setups, or barely weeks into reopening, so every dollar is crucial. Many had anxiously anticipated the season, which began in early March and will wrap up in the next week or so, as a barometer for post-hurricane success. There are other pressures on Florida’s retail and tourism industries: Inflation and the threat of punitive tariffs have rattled the American economy. But in the Tampa-St. Petersburg region, few can remember a hurricane season as disruptive as last year’s, when Hurricanes Helene and Milton delivered a one-two punch just 13 days apart. Advertisement SKIP ADVERTISEMENT Some businesses and hotels remain closed, and local governments have been swamped with post-storm requests for building permits; many have expedited the process by waiving fees or setting up temporary remote sites to process claims. More than 8,000 emergency rebuilding permits have been issued in St. Petersburg alone, for an estimated $150 million in construction value. Hurricane Helene, in particular, “was a very humbling experience,” said Savannah Huskie, 28, a manager at the Bronze Lady, a boutique along the John’s Pass Boardwalk in Madeira Beach that flooded. The store had to close for two months and between the damage, the wrecked merchandise and the closure, lost hundreds of thousands of dollars. The ocean is both the greatest draw and the worst threat along the Gulf Coast. But hurricane season does not begin until June, making spring visits more appealing for many out-of-town visitors. “Spring break is our season, more than summer,” said Charlotte Hunter, the co-owner of Wild Time Caribbean, a store along the boardwalk in Madeira Beach that sells beach apparel and a menagerie of stuffed manatees and turtles. The store had to cancel merchandise orders in the immediate aftermath of the hurricanes, when there was still sand and debris piled in the roads and along the streets. “That’s why spring was so important for us — to recoup some of that,” said Ms. Hunter’s husband, Jim Hunter. The slow trickle at the start of the season gave them pause, and their door count was down by about 1,500 people for the second half of March. But it was unclear, the couple said, whether that was also influenced by inflation and a shaky economic outlook. Signs of recovery were everywhere. The city of Treasure Island held a new festival, “Back to the Beach: Sand & Kites & Coastal Delights,” last month after canceling several events over the fall and the winter. Storm debris was largely cleared away so that visitors and locals alike could safely walk along the streets and shorelines. Permits were approved so that businesses could legally operate outside of their damaged buildings, allowing them to reopen while they wrestled with bureaucratic paperwork. Still, there had been a lot of anxiety about whether anyone would show up. “There was a lot of question marks,” said Stephen Santasieri, the general manager at Caddy’s, a popular beach-front restaurant and bar in Treasure Island. Its building was flooded during Hurricane Helene, and snarled pipes and frayed wood were still exposed . Mr. Santasieri estimated that it would take at least a year to rebuild. Caddy’s spent three weeks of spring break serving $8 Patron cocktails and $10 margaritas (with a free gift) from a makeshift outdoor setup. Its kitchen is operating out of a food truck, without its usual fresh grouper and oysters. Rather than scribble their names on a strip of wood along the restaurant’s bar, a tradition at Caddy’s before the storm, customers have instead signed a banner hanging nearby. “People have really appreciated it,” Mr. Santasieri said. “They’re just happy to see it back.” In recent weeks, pink and purple bougainvillea bloomed near storm-battered sea grape bushes and palm trees. Beachgoers with rosy shoulders carried bags of snacks past construction workers repairing roofs. Some visitors came only after calling their hotels or their favorite haunts for assurance that they were open. Others had forgotten that the storms had even passed through. “I wasn’t even thinking about it,” said Lubomira Paskaleva, a teacher visiting from Kansas City, as she walked along the beach in Treasure Island, seashells in hand. “Why wouldn’t we want to go?” The owners of the Airbnb she was staying in appeared to be raising the house with more pilings, she said, but it did not detract from how beautiful the beaches were. For many, the emotional and financial pain of navigating the hurricanes’ aftermath remains acute. John Messmore, who owns Sweet Sage Cafe in North Redington Beach, said that after the floodwaters of Hurricane Helene reached more than three feet inside, “everything was upside down and floating in salt water.” He spent the next few months wrestling with all the paperwork needed to get a building permit. Hundreds of thousands of dollars were spent just to replace four 80-foot trees behind the cafe, let alone the furniture and supplies inside. “It would have been much easier to turn around and walk away,” said Mr. Messmore, 81, wearing a hat with “Relax” embroidered in gold thread across the front. But, he added, “I just had to make sure it was put back together right.”

Residents across a broad stretch of the Northeast woke up on Saturday to snow blanketing backyards and frosting trees, just as the pastel colors of Easter promised that spring was near. An area stretching from around Albany, N.Y., to Maine experienced moderate snowfall, mostly from two to five inches, overnight Friday into Saturday morning, according to the National Weather Service. And while spring technically started on March 20, snowfall at this time of year is far from rare. “In upstate New York, you know, a couple inches here and there is certainly not unheard-of, even in the early spring,” said Abbey Gant, a meteorologist with the Weather Service office in Albany. While the Weather Service reported a trace of snow at LaGuardia Airport, there were no reports of snow in other parts of New York City. Advertisement SKIP ADVERTISEMENT In Maine, where two to five inches of snow had fallen by Saturday morning, Michael Clair, a Weather Service meteorologist, said that the snow was “nothing we haven’t seen before.” It’s also something the state might see again before warmer weather moves in. “It’s still too early to say we’re done for sure,” Mr. Clair said. “This is sort of what our spring looks like. It’s a mix of things.” Snow was expected to continue through Saturday, tapering off as the day progressed, before the region dries out next week, forecasters said. For Jill Woodworth, 58, who grew up in Connecticut and has lived in Orange, Mass., for the past 25 years, waking up to snow in April can be routine, but it’s still shocking. “I’ve lived in this area for most of my life, and it’s not unusual, but it’s just like, ‘Oh my God,’” Ms. Woodworth said. “It feels like it’s been a long ramp up to spring with the flowers and the trees.” Editors’ Picks How Pickle Lemonade Took Over the Group Chat Kristen Stewart Thinks the Critics at Cannes Are Being Too Nice Living the Slop Life Ms. Woodworth said she remembered past Aprils when up to two feet of snow had fallen. This time around, she estimated that only about two inches had dusted her backyard, with no need to shovel any snow. “I’ll brush off the car, though,” she said, “before I go get Dunkin’.”

As stocks gyrate in response to President Trump’s on-again, off-again tariffs, the world is understandably focused on the immediate chaos affecting the global economy. Yet over the past few months a number of signals have pointed to a far more profound disruption on the horizon: the growing economic cost of climate change. In a recent report about the rising demand for air-conditioning, Morgan Stanley casually observed that the planet was all but certain to blow past the goal of limiting the global average temperature rise to no more than 2 degrees Celsius above preindustrial levels, a threshold laid out in the Paris Agreement. The company’s “base case,” the report said, was that the world was moving toward a temperature increase of 3 degrees Celsius. That forecast, once thought of as extreme, is now becoming commonplace. The United Nations’ Emissions Gap report for 2024 said that the world was likely to warm 3.1 degrees Celsius over the course of this century without efforts to rapidly reduce emissions. The Intergovernmental Panel on Climate Change has forecast that without drastic action temperatures will be even higher than that by the end of the century. A constant challenge when talking about global warming is appreciating that little numbers — a rise in temperatures by just a single degree, for example — represent utterly profound changes. Which is why it’s worth pausing to consider what scientists have said about what the world would look like if average global temperatures rose 3 degrees Celsius, and what it will cost. A planet transformed At 3ºC of warming, rising seas are likely to inundate many coastal cities, including metropolises like Rio de Janeiro, Shanghai, Miami and Osaka, Japan. A litany of other problems, including extreme weather, unrelenting heat waves, the proliferation of insect-borne diseases, widespread species extinction and declines in crop yields, would also get worse. It’s impossible to know the actual cost of all these disruptions. Yet as the prospect of more intense warming becomes more likely, some estimates are beginning to emerge. By 2049, costs from the effects of climate change could total more than $38 trillion annually, according to a paper by scholars at the Potsdam Institute for Climate Impact Research. In the United States alone, climate change is expected to wipe away $1.47 trillion in value from real estate around the country by 2055, according to a February report from First Street, which models climate risk. Just in New York City, more than 80,000 homes could be lost to floods in the next 15 years, my colleagues Mihir Zaveri and Hilary Howard reported this week. Beyond the immediate losses inflicted by severe weather and flooding, a decline in output is likely as crops fail and extreme heat strains supply chains. Researchers at ETH Zurich recently calculated that in a world that has warmed 3ºC, global gross domestic product is likely to fall by an average of 10 percent, with poorer countries hardest hit.

Phoenix hit a scorching 100 degrees Fahrenheit on Thursday, notching the city’s first triple-digit temperature of 2025 nearly a month before it typically reaches that high. And it’s far from alone: An area across the Southwest from Southern California through the Central and Northern Plains is expected to have temperatures spike between 10 and 30 degrees above average this week. This rise in temperatures is being driven by a huge high pressure system that has settled across much of the western United States. Acting like a lid on the atmosphere, it traps heat near the ground and keeps clouds and rain away, resulting in a large supply of sunshine that allows temperatures to soar. “That area between Los Angeles all the way to Phoenix is where you’ll see your well-above-normal temperatures,” said Scott Kleebauer, a meteorologist with the National Weather Service’s Weather Prediction Center. Phoenix is known for its sweltering summers, but on average it reaches its first 100-degree day on May 2. But it’s already been a warm spring for Phoenix, which hit a record-breaking 99 degrees on March 25. This week, the Weather Service expects the intense heat to linger, with temperatures remaining at or above 100 degrees through Saturday, and some daily record highs most likely being broken, too. On Friday, Phoenix is forecast to reach 102 degrees, and 100 is expected again on Saturday. The Phoenix office of the Weather Service has warned of a moderate heat risk for lower desert communities, saying that the extreme heat could lead to heat-related illnesses, especially among vulnerable people. The experts have advised local residents to stay hydrated, limit their time outdoors during the afternoon, wear lightweight and light-colored clothing, and to check on older neighbors, children and pets. ‘Spring is flexing its muscle.’ The Weather Service said highs in the 70s, 80s and 90s were expected through Saturday across the Southwest, and into the 90s and 100s across portions of the Southern Plains. At the same time, much of the eastern United States is experiencing a stark contrast, with cool, wet and stormy weather, driven by a different system moving southward. “Spring is flexing its muscle,” Mr. Kleebauer said. “You have a period, usually around mid-to-late March and it carries through maybe even most of April, where both winter and spring are kind of fighting back.” He added that while this pattern wasn’t unusual for spring, the strength of the divide between east and west, and the early occurrence of the extreme heat in the Southwest were “definitely an anomaly.” The risk of wildfires is also expected to go up this weekend in the Southwest. The Storm Prediction Center’s fire weather outlook warns that strong winds and dry conditions, driven by a system moving through the northern Rockies and into the Dakotas, could increase the risk of wildfires for much of the Desert Southwest. Some relief is on the horizon starting Sunday, when temperatures are expected to ease into the upper 80s or low 90s. “These well-above-normal temperatures across the Southwest into the Southern Plains will kind of linger all the way through Sunday,” Mr. Kleebauer said. “And then things start to finally cool down a bit in those areas as we head into early next week.”