The record-setting heat wave in Phoenix this summer, thirty-one consecutive days of temperatures exceeding a hundred and ten degrees, finally broke on Monday, July 31st. But, by the following Friday, August 4th, the thermometer was creeping up toward a hundred and fifteen degrees. Residents liked to joke that anything below the “teens” was comfortable. Jessica Lindstrom, who was thirty-four, was no longer a resident. She and her husband, Daniel, had bought a house in Central Point, Oregon, in 2015. But she had grown up in greater Phoenix and, that week, had brought her expanding family to Arizona to stay with her parents. The next day, they were going to celebrate the baptism of their second-oldest son, in the chapel of the Church of Jesus Christ of Latter-day Saints.

Lindstrom was relieved to have her parents’ help. She might not have wanted to admit it—she could be a perfectionist, and her family called her a supermom—but she was exhausted. In Oregon, not only was she raising four young sons (her oldest was just ten) but she was also a nurse, working night shifts at a hospital, in an in-patient rehab. In between, she ran the children’s religious-education program at her local church. Her husband worked full time as a pharmacist. So, that Friday morning, happy to be home, back in the desert, she decided to take some time for herself. At 8:30 A.M., while her parents watched the kids, she headed to the nearby Deem Hills Recreation Area—a small mountain, scratched over by hiking trails.

Deem Hills covers nearly a thousand acres of the Sonoran Desert, and is known for its unique basalt volcanic-rock formations. The rock holds the heat, meaning that the ambient temperature, what Lindstrom actually felt, could have been ten degrees hotter than that day’s high of a hundred and fifteen. The longest trail—a circumference of the entire ridge—is just under six miles. Lindstrom had hiked these hills countless times. She loved the open sky, the desert colors, the towering saguaros, with their arms open wide. She loved the quiet, and the sense of peace she felt, nestled in the tiny valleys, or when she stopped to take in the view, looking out over her home town. One of the hike’s orienting landmarks was the steeple of a Latter-day Saints temple. Daniel, who is from California, often hiked with her there after they started dating, and he grew to love the hills, too. On a hike in 2012, he got down on one knee, and, “in the corniest possible way,” as he described it to the family later, asked Lindstrom to marry him.

Daniel, an élite runner (he was on the cross-country team at the University of California, Riverside, and had completed several marathons), had gone running in Deem Hills earlier that morning. Lindstrom met him at the park before her run, and he continued to his in-laws’ house. She left her phone in her car. Her long brown hair was pulled back in a ponytail, and she wore a black tank top, neon-yellow shorts, and sneakers.

Around 10 A.M., the family grew concerned that Lindstrom hadn’t yet returned. Daniel and two of Lindstrom’s brothers went to check on her. By eleven-thirty, her father, David Adams, and her third brother had joined the search. Her mother called 911. A member of their church is a captain with the Phoenix Police. He quickly organized a search party with the fire department, using helicopters, drones, and men on the ground. The police posted a missing-person sign online, and social media filled with calls for volunteers. Adams called his only daughter Peanut, but Lindstrom was a strong athlete, tough and persistent. It seemed unimaginable that she could have just vanished.

Globally, about half a million people die from heat-related causes every year, according to a 2021 study published in The Lancet Planetary Health. Across the U.S. each year, significantly more people die from heat than from any other weather-related event, including hurricanes, tornadoes, floods, and even rip currents. Many of these deaths are concentrated in and around Phoenix. In 2022, there were four hundred and twenty-five heat-associated deaths in Maricopa County—a twenty-five-per-cent increase from the previous year. The impacts of this year’s heat wave are still being analyzed. But, for everyone who lived through it, this was a relentless thirty-one-day emergency, with no respite. “We’ve hit these highs before,” Nick Staab, the assistant medical director for Maricopa County’s Department of Public Health, told me. “But now, it’s just not having a break. The human body needs an opportunity to cool down.”

People have inhabited and thrived in the Sonoran Desert for centuries. In 1050, the Sinagua, a name that came from the Spanish, meaning “without water,” made cliff dwellings in the Verde Valley, just ninety minutes north of central Phoenix. Their homes and structures were constructed with wood, stone, and mud and built into the walls of a limestone ravine, extending through a system of caves, which tend to be cooler than the outside air in the summer. The ravine walls faced south, meaning the dwellings would have stayed warm in the winter. In the nineteen-seventies, an Italian architect named Paolo Soleri built his own south-facing labyrinthian cliff dwelling into the side of a mesa outside Phoenix, hoping to construct a new kind of ecologically and desert-mindful city. Arcosanti, as he named it, still exists, with some fifty residents, and tourists year-round. But Soleri’s vision seems as lost as that of the Sinagua.

In the early twentieth century, the invention of air-conditioning allowed a city to grow rapidly, in ways that no longer heeded the desert heat. In recent decades, farm fields and open desert have been replaced by roads, parking lots, cars, strip malls, and endless subdivisions, leading to an urban heat island, which compounds the effects of the climate crisis. Maricopa County, which contains Phoenix and more than two dozen other cities, towns, and tribal communities, is now the fourth most populous county in the United States. Phoenix is the fifth-largest city in the U.S., and the hottest large city, with an average summer temperature of 93.7 degrees—an average that has increased by 3.8 degrees since 1970. Nighttime summer temperatures, largely owing to urbanization, now average a low of eighty-three degrees, an increase of 5.4 degrees since 1970. Even the saguaro cacti, which are endemic to the Sonoran Desert, can’t cool off enough at night. They have been dropping their arms and falling down.

And, yet, people continue to flock to Maricopa County, the fastest-growing county nationwide last year. People might dislike the summertime heat, but it’s a small price to pay for the other eight gorgeous months of the year. “The key, for the summer, is not to be here,” a Phoenix firefighter and lifelong resident told me.

People who can’t afford to leave must adjust. Runners and cyclists invest in headlamps and glow-in-the-dark gear. Construction workers start their days at 4 A.M., bringing in giant floodlights to work sites. Since pools get too hot for swimming, homeowners buy giant ice blocks for pool parties. Pedestrians carry parasols. Parking attendants sit outside next to swamp coolers. Restaurants and bars deploy fans and misters, shrouding their patios in a cool fog. (In deep summer, even the misted patios are empty.) One outdoor bartender told me that fans under the bar “keep us alive, mildly. And tequila shots.”

The streets seem abandoned, save for the unhoused. People go from air-conditioned houses, to air-conditioned cars, to air-conditioned offices, stores, schools, or camps. They get used to seeing their car dashboard thermometer read a hundred and twenty if it’s parked in the sun in the afternoon. They take care not to sear themselves when touching car-door handles. (I burned my leg on the side of a car door.) Shade becomes sacred. “It’s kind of the opposite of how other areas hibernate,” Sonia Singh, a spokeswoman for the Department of Public Health, told me. “We go outside in the winter and come inside during the summer.”

Still, this summer, which included the hottest July ever recorded on the planet, has been different. Not only were the days scorching but there was a stretch of sixteen days when the nighttime low was ninety degrees or above, including one night when the low was ninety-seven degrees. Summer is supposed to be monsoon season in Arizona, but by mid-August the Phoenix Sky Harbor International Airport hadn’t recorded measurable rainfall in a hundred and forty-seven days. Arizona’s only burn center, situated in Phoenix, was full of patients who had fallen on the ground and burned their skin. The Maricopa County Department of Emergency Management took to holding “FRYdays” on Twitter, cooking various foods—cookies, pizzas, roasted red peppers—on dashboards, to show how hot a car’s interior can get, in a lighthearted effort to remind people to avoid the heaviest kind of risk, a calamity that continues to happen: pets and children being left in hot cars.

The city of Phoenix established an Office of Heat Response and Mitigation, the country’s first publicly funded city-government office working on heat, in 2021, and appointed an energetic young scientist named David Hondula to run it. (Miami and Los Angeles also have chief heat officers.) “We’re writing a playbook for jobs that haven’t existed before, and we’re trying to do so as quickly as we can,” Hondula told me. “Obviously what we’ve experienced this summer is not anything the region has experienced before.”

As temperatures increase worldwide, heat’s invisible danger will threaten more and more people. By 2030, according to a new climate analysis from the Washington Post and the nonprofit CarbonPlan, four billion people will be exposed to at least a month of extreme heat. (In dry climates, like Phoenix, that could mean a month of days reaching a hundred and twenty degrees Fahrenheit or higher.) By 2050, that number will increase to five billion, or more than half the planet’s population. So far, the Maricopa County Office of the Medical Examiner has confirmed a hundred and eighty heat-associated deaths this year, with three hundred and thirty still under investigation. Both numbers are much higher than those at the same time last year, despite a lag in the data, since it takes about six weeks for the O.M.E. to conclude a death investigation. The O.M.E.—already one of the busiest medical examiner’s offices in the U.S.—has been overwhelmed.

One morning in August, I arrived at the Forensic Science Center, the O.M.E.’s headquarters, to meet with Jeff Johnston, the chief medical examiner, who was rail-thin, wearing black-rimmed glasses, a gray beard, and a gray suit. He spoke about his work softly and kindly, with a subtle drawl, having grown up in the Southeast. He did his pathology residency at the University of Tennessee, in Knoxville, and worked in the university’s forensic-anthropology facility (commonly known as the Body Farm). He saw his profession—which, to his great frustration, is struggling to recruit enough people—as a critical form of public service. “By understanding what people died from,” he told me, “we can have this huge impact on preventing future deaths.”

Johnston was accompanied by one of his investigators, a wide-eyed twenty-six-year-old named Emily Sprague, who had very long, straight blond hair. They both carried giant water bottles. Sprague’s job is to take a report about a decedent from the first responders, then drive to the scene, investigate the environment and the body, and coördinate the return of the body to the Forensic Science Center. (On such trips, Sprague and the office’s other death investigators wear “cool” vests, which have pockets stuffed with ice packs.) “We’ve just gone through a historic surge,” Johnston said. “We had to push everybody to the limit in order to respond.” This meant they had less time to find and notify next of kin. If they couldn’t release bodies, their refrigerators were at risk of filling up. At the end of July, as an emergency precaution, the office trucked in portable refrigerators, as it did during the city’s worst COVID surge. (In the end, the office did not need to use them.)

Heat illness happens in two ways. The first is classic heatstroke, a result of prolonged heat exposure, which typically strikes infants; the elderly; those who are overweight; and unhealthy, sedentary adults, who may be suffering from other chronic conditions such as cardiovascular disease, diabetes, or hypertension. It’s what kills a person stuck in a house with malfunctioning air-conditioning on a summer day. The second type of heat illness is exertional heatstroke, which occurs during physical activity. “So you can get this,” Johnston said, pointing at me. “Anybody can get this.” The risks are highly individualized. Respiratory problems, prescription or over-the-counter drugs, alcohol, even scars on the body, can affect how a person regulates heat. Young, fit people, such as long-distance runners, are more capable of warding off the warning signs of heat illness until, sometimes, it’s fatally too late. Acclimatization matters. In the desert, for instance, visitors are not only unaccustomed to the heat, they don’t realize how much fluid they are losing just by breathing and talking in the dry air, which leads to dehydration, then reduced blood volume, exacerbating heat exhaustion.

In the hot sun, or a very hot dwelling, the body must work to maintain its normal internal temperature, generally about ninety-eight degrees. The heart starts pumping more blood to the skin, where it can cool down. You will start sweating profusely, and might experience cramps or nausea. If you cannot find a way to cool off, your core temperature will quickly increase, forcing your heart to beat faster, which increases your metabolism, and generates more heat. As blood is diverted away from your internal organs, including your brain, they become starved of oxygen. You will feel dizzy, or faint. Once your body temperature rises above a hundred and three, heatstroke can begin. Sweating stops, and the skin will turn red, hot, and dry. Your head will throb. As the blood pressure falls in your brain, you will probably pass out. Sprawled, unconscious, in the hot sun, you will continue to overheat. Once your body reaches a hundred and five or a hundred and six degrees, your limbs might convulse, and, at a hundred and seven, your cell membranes melt, and proteins inside the cells unfold. Organ function starts to shut down; muscle tissues begin to disintegrate. It becomes increasingly difficult to cool you off fast enough to save your life. The heart just stops.

Still, for forensic pathologists, it can be difficult to identify heat as the primary cause of death. There is nothing specific that signifies a person died from heatstroke, apart from the environment in which the person was found. But Johnston’s office has always had a rise in “admissions” (deaths to investigate) in the summer months. From 2013 to 2021, in Maricopa County, the month of July averaged twenty-four-per-cent higher admissions than in non-summer months. But, in 2022, July saw a sixty-per-cent jump. This year, there were eight hundred and forty-two admissions—a seventy-eight-per-cent jump. “It is a substantially larger surge than we’ve ever seen,” Johnston said.

The scenes that Johnston’s team of investigators encountered this summer were exceedingly challenging. They found bodies sprawled on asphalt, curled up in tents, collapsed in back yards. At one deceased man’s home in August, where the air-conditioning was not functioning, the temperature was roughly a hundred and thirty degrees. Sprague told me that she had conducted many investigations a couple of blocks down the street, in the Zone, a large homeless encampment surrounding a cluster of outreach organizations. Unhoused people were the victims in more than half of confirmed heat-related deaths in Maricopa County in 2022, and two-thirds of those deaths involved drugs or alcohol. Sergio Armendariz, a case manager now working for a Christian nonprofit organization called the Phoenix Rescue Mission, told me that, during a half decade spent living on the streets, he started using heroin, and smoking meth. “It made sense for me to just be high all the time, because I didn’t have to eat, and I could stay awake at nighttime,” he said. “So, eventually, I started slamming it into my veins, too.” Meth allowed him to cope. “You’re numb to everything.”

I met Armendariz—a strong, smiling, relaxed man in his mid-thirties, wearing a Diamondbacks cap backward—next to a dumpster, in a large church parking lot. He was overseeing a landscaping and street-cleanup program that he started last year, specifically to give the unhoused a stepping stone toward housing and employment. That morning’s group of workers had just arrived to empty a truck bed full of litter and brush. A few mornings each week, a Phoenix Rescue Mission van—well supplied with water and ice—picks up a group at 5 A.M., in order to beat the worst of the heat. The workers finished emptying the truck, and walked over. “A lot of the parks have turned their water off,” a sixty-four-year-old woman named Jennie Gaudioso, who had long, wavy, gray-brown hair, said. Her mouth was trembling.

“I live in front of Q.T.,” a tall, skinny young man named Alan Miskiewicz said, referring to QuikTrip, a gas-station chain. “It’s close to water and stuff. They kick you out of the park.”

“We’re looked down on,” Gaudioso said. “But they have to remember they could be us.”

On Friday, August 11th, as the death toll increased, Arizona’s Governor, Katie Hobbs, declared an extreme-heat state of emergency, allocating funds for grid-resiliency projects and opening two new cooling centers near the state capitol. During the hour I visited, several unhoused people came through to get water or snacks, or to watch television.

Currently, because heat is not considered a major natural disaster, there is no mechanism by which local offices, including Johnston’s, can easily get federal support during a surge of heat deaths. In June, the Arizona congressman Ruben Gallego, with two other legislators from Texas and Nevada, introduced a bipartisan bill to add extreme heat to FEMA’s list of major-disaster qualifying events. This would provide the O.M.E. one path for requesting help from the federally directed Disaster Mortuary Operational Response Teams, or DMORT, which is made up of forensic dentists, pathologists, anthropologists, DNA specialists, funeral directors, and medicolegal death investigators. Some staff members from Johnston’s offices are on standby with DMORT, including their forensic dentist, who received a request to respond to last month’s deadly fires in Maui. Johnston told me, “He’s, like, ‘No, I can’t go, I’m identifying bodies here in Phoenix.’ ”

Ty Wade, a self-taught artist, was at a studio, sketching a charcoal portrait, when he got a text from a friend. “There’s a woman missing after going for a run at Deem Hills at 8am,” she wrote, sending screenshots of the Lindstrom family’s social-media posts from earlier that afternoon. “Sounds like they are asking for volunteers to search . . . the mountain area.” Wade, who is from Arizona, had served twenty-four years in prison for a murder he got caught up in with a friend, in New York, when he was only sixteen. (He had pleaded guilty, but was tried as an adult and sentenced to thirty years without parole.) He was released in April and relishing his freedom back home with family in Arizona. He wanted to make his time count. He texted his friend back, “Fuck it I will go.”

Lindstrom’s father and her brothers had already been searching for hours. Firefighters and police had responded to the scene first, around 12:30 P.M. Technical rescue teams circled the mountains, and flew drones. Around the same time, friends, family, and strangers from the community, eventually numbering in the hundreds, went to Deem Hills, to support the family, with water, food, and logistics. A friend took Lindstrom’s mother’s phone, to field calls and texts. Another friend watched Lindstrom’s four sons back at her parents’ house.

Wade drove ten minutes from his studio to join the search. He met Lindstrom’s father in the emergency staging area. Wade had never been hiking in the area, but he knew the desert, and, at first, couldn’t believe that no one had found Lindstrom yet. There seemed to be nowhere to hide. Deem Hills was surrounded by upscale subdivisions and small shopping centers. As the bird flies, a hiker is often barely a mile from safety.

But, high up the mountain, Wade found the terrain treacherous. He had to circle carefully around rocks and thick vegetation to make sure someone wasn’t lying on some unseen spot of the desert floor. He stayed within a relatively small, steep range, and zigzagged up and down. Eventually, he returned to camp to hydrate. He had become dizzy from the heat before, and knew its risks.

Around six in the evening, another volunteer found Lindstrom. Wade had been searching very close to where she was, possibly just yards away. She was off the trail, on the north side of the mountain, lying between a large rock and a paloverde tree, a desert species with pastel-green, photosynthesizing bark. She had no water with her. Others on the hill heard the searcher’s cries, and rushed toward them. Lindstrom’s husband and youngest brother arrived before the police. She was unresponsive. Emergency responders showed up, and confirmed, with a heart monitor, that she was beyond resuscitative efforts. Lindstrom was pronounced dead at 7:14 P.M. The O.M.E. investigator arrived shortly thereafter to prepare a report of the scene. Captain Scott Douglas, of the Phoenix Fire Department, told reporters that her death was likely a consequence of heat exposure. “Unfortunately, Mrs. Lindstrom was in town from Oregon, where it doesn’t get this hot,” Douglas said.

Given the location and position of Lindstrom’s body, on the side of the mountain, there was concern that she had taken a fall. The O.M.E. report, which was finalized a little more than a week ago, confirmed that she had abrasions on her head, neck, torso, and limbs, and had dislocated her neck. She was dehydrated. The medical examiner determined that accidental blunt-force trauma of the head and neck had caused the death. Environmental heat exposure was a contributory cause. While no one will ever know the exact order of events, it is highly likely that Lindstrom passed out from the heat, fell, and hit some rocks.

Two weeks later, on a cloudy Saturday morning, Lindstrom’s family held a funeral at the Church of Jesus Christ of Latter-day Saints in Glendale. For the first time since June 13th, the valley failed to reach a triple-digit temperature. The meeting room where the funeral was held was connected to a gymnasium, where the basketball hoop was raised to the ceiling. By 10 A.M., the entire space was filled with mourners. Two police officers stood in uniform at the back. Lindstrom’s casket, covered with an enormous fan of colorful flowers, stood before a simple wood stage. I sat near Wade, who stood out among the gathered, during the service. His shaved head, part of his face, and his arms were covered in tattoos—a way to practice his art, pass the time, and learn a new trade while in prison. I noticed him wiping away tears.

After Lindstrom’s service, the family went to the graveyard, and church members prepared the gym for a luncheon, setting up a buffet with roasted ham and salads, and placing a picture of Lindstrom, a plant, and some jelly beans on each table. Wade stood outside in the hall, and spoke to another man who had searched the hills on August 4th. “It was a brutal day,” Wade said. He had wanted to help save Lindstrom’s life. Down the hall, in the entrance lobby, among many photos of Lindstrom and her family, there was a large, framed, charcoal portrait of Lindstrom, which Wade had made for the family. “This is part of my chance to give back,” Wade told me. Prompted by his involvement in the search, he had joined the Red Cross. He will soon begin training sessions to become a member of their volunteer-based Disaster Action Team, and, through a separate organization, he is planning to partner with a search-and-rescue dog.

Lindstrom’s parents, David and Angela Adams, approached. “We meet again,” David said to Wade, shaking his hand with both of his own.

“I’m humbled,” Wade started to say.

“Many people have made comments about it,” David Adams said, referring to the charcoal portrait. “Appreciate you.”

A few more condolences were exchanged. “Most people don’t pass in such a public way,” David Adams told me. “But, for some reason, Jessica did. We were on the mountain looking. We looked at all the trails. It wasn’t until the community pulled together, and the volunteers came, like Ty, looking for her. One of them found her. We’re so grateful that they did.” ♦