This Is How You Die of Extreme Heat

“At least 14 Tarrant County residents died from extreme heat last summer … Of those who died from heat, at least eight cases included residents with no air conditioning, no working air conditioning, or who had their air conditioning turned off at the time of their death…” –The Fort Worth Star-Telegram, June 25, 2023

98.6 Fahrenheit

Air conditioners aren’t supposed to make that sound. The gray-white box in the window had always rattled, but this morning it has begun to grind. The grandmother puts her hand in front of the AC’s dust-covered gills, feels nothing but a weak, lukewarm breeze.

She thinks about calling her daughter, whose husband installed the unit in her trailer’s living room window the summer before. She shakes her head to herself: No, they have the baby; it’s a 40-minute drive; she’s a burden enough as it is. She doesn’t have internet in the trailer to see the day’s excessive heat warning. Her cell phone, another gift from her daughter, is dead more often than it’s not, and she can’t find the weather app on it half of the time, anyway.

But the grandmother has been hot before — prides herself, even, on her 68 Texan summers. Besides, she’s not planning anything strenuous today, which would elevate her chances of exertional, or “activity-induced,” heat stroke — the kind that makes the news for killing the young, fit, and healthy, like the California couple who were found dead on a trail with their 1-year-old baby and dog in 2021, or the stepfather who died last month while trying to rescue his 14-year-old stepson, who also died, while hiking in 119-degree weather in Texas’ Big Bend National Park. Like the dozens of promising high school and college athletes who collapse during training, games, and meets every year.

Or like the characters in longtime Outside correspondent and adventure historian Peter Stark’s cautionary tales about succumbing to the elements. Stark is perhaps best known for his second-person narrative about what it’s like to die from hypothermia, which recirculates every winter, but he has a particular, morbid fascination with heat strokes, having now written two different versions (a competitive cyclist dies in one; a hungover, hiking surfer is brought back from the brink in the other). “Out of all the research I’ve done into ways to die — or come close to dying — heat stroke is the one I found the scariest,” Stark told an Outside interviewer last year.

Like Stark’s characters, the grandmother is fictional and illustrative. Unlike Stark’s characters, she has not elected into risk. Exertional heat stroke is often described as “sporadic” because it is circumstantial; it is also less deadly since an athlete often begins to feel terrible, or collapses, before the point-of-no-return. “Classic” heat stroke, which results from unbearably high temperatures, “occurs in epidemic form” in the sense that it strikes the vulnerable at once and all together: the ill, the elderly, the unhoused, the bedridden, the prepubescent. Though heat-related mortality can be hard to pin down, by some estimates classic heat stroke is fatal in over 60% of intensive care cases — part of the reason extreme heat is credited as the deadliest weather phenomenon in the United States.

The grandmother goes to her sink and fills a glass of water. She looks out the window, at the tall grass growing alongside her neighbor’s trailer, and thinks about her grandbaby. Her trailer, which had stayed cool overnight before the AC conked out, has already begun to feel muggy, but she isn’t alarmed.

It is 97 degrees outside and getting hotter.

99.5 Fahrenheit

The human body is a contradiction: It can run a marathon in under two hours; it can scale the tallest mountain in the world; and it can survive episodes of extreme cold and starvation. At the same time, it is hilariously delicate: Only about 8.2 degrees separate our core body temperature of 98.6 from multi-organ dysfunction, which begins somewhere around 106 degrees, depending on the person and circumstances. Because this leaves little margin for error, our bodies spring into a well-rehearsed response when blood warmed by our environments at the surface of our skin makes its way to our brain, causing our hypothalamus to rustle through its bag of cooling tricks.

The grandmother’s body begins to run through them as the trailer’s temperature rises to 100 degrees, the point at which the body ceases to give off heat and begins to absorb it. Her hair follicles relax to release any trapped warm air against her skin. Her sweat glands are activated, and soon she’s covered in a light sheen that serves to transport heat away from her body via evaporation. Crucially, her blood vessels dilate so that the warmed blood can pass closer to the surface of the skin, where it will ideally be cooled by the heat pulling away from her body.

But as an older adult, the grandmother’s blood vessels don’t dilate as well as they used to. Her body strains to cool itself and her heart pumps harder. And despite her glass of water, the grandmother begins to notice she feels … off. She is experiencing some of the most common heat-related symptoms, the ones most of us are probably familiar with: Her stomach starts to cramp and she feels slightly nauseous as blood is redirected from her gut to the surface of her skin. She begins, also, to feel fatigued — unbeknownst to her, the drowsiness is because her body is running its cooling mechanisms full-blast, compensating for the broken AC.

But today, these systems are fighting an uphill battle. The trailer is humid, meaning the grandmother’s sweat isn’t evaporating as efficiently as it would in dry air. She has a sunburn from sitting on her lawn the day before, and her body is using water to try to heal it, leaving her with less liquid overall to sweat out. She can’t drink enough water to replenish what she’s lost, either, since the human body can only absorb, at max, one liter of water an hour, and those in extreme heat conditions can lose that or more in the same span of time.

Little does the grandmother know, either, that because it’s now over 95 degrees in her trailer, the fan she’s turned on is no longer having any cooling effect. Her core temperature tips toward 100 degrees.

102.9 Fahrenheit

Heat exhaustion sets in when the core body temperature is between 101°F and 104°F, as the grandmother’s is now. (Core body temperature cannot reliably be read on an oral thermometer, which is part of why the Centers for Disease Control and Prevention recommends watching for symptoms of heat exhaustion and heat stroke rather than taking your own measurements). In addition to her fatigue, she now feels dizzy. Her heart is pounding as her body tries to regulate itself; if she had a preexisting cardiac condition, she would be in even more danger than she already is. She stands up to get more water and feels a woosh of lightheadedness — a result of low pressure stemming from her dilated vessels — and her vision momentarily goes black. She nearly faints, but steadies herself with a hand on the back of a chair.

If a neighbor checked in on her, as the weathermen on TV are advising good samaritans do, they would see that the grandmother looks pale, that she’s grown irritable and unfocused. The neighbor might suggest she take a cold shower before asking her to come to their air-conditioned trailer, or a local cooling center, for the rest of the day. The most crucial thing, though, would be that she gets to a safe temperature, and fast, before her core hits 104, the threshold of heat stroke.

105.1 Fahrenheit and climbing

In her delirium, the grandmother thinks to take an Advil, foggily hoping a fever-reducer might help lower her core body temperature. And though the damage wrought by extreme heat is similar internally to that inflicted by a dangerously high fever, the response systems at play in each case are completely different. For extreme heat, there is no magic pill, no shut-off switch for how the grandmother is feeling aside from getting somewhere cool.

It might seem like a simple thing: getting somewhere cool. In this sense, classic heat stroke is, agonizingly, preventable. Though most Americans have air conditioning, over a quarter — 34 million households — “said they could not [financially] meet their energy needs at some point” during 2020, according to Energy Information Administration data. Of those who were struggling, 10% reported enduring dangerously high temperatures in their homes due to concerns about cost.

Because Americans typically do have access to AC, though, losing air conditioning for reasons beyond their control — say, due to grid failure, a localized blackout, or a mechanical issue — actually makes people more susceptible to dangerous heat-related illness, in part because acclimation has such a large role in how well we tolerate heat. The shock of living in climate-controlled rooms and suddenly finding yourself without one can be deadly.

The grandmother’s internal temperature is now over 105 degrees and still rising; she is well within the realm of heat stroke. Her pulse is rapid and now she is confused and agitated — she stumbles, directionless, toward her living room and collapses on the floor. Her body is rationing water away from vital organs, like her kidneys, which begin to shut down. Her brain is swollen. She cycles in and out of consciousness on the floor.

Her body is past the point of being able to bring its temperature back down by itself. A heat stroke victim may stop sweating. Their cells begin to die — the cerebellum, which controls motor functions, is one of the earliest parts of the brain to fail. They may have seizures or hallucinate or, nearing the end, feel a soaring sense of euphoria. Internally, the body is in freefall; by one estimate, there are 27 different pathways to death once heat stroke sets in, ranging from heart failure to the proteins that control blood clotting becoming overactive and cutting off flow to vital organs.

When the grandmother’s daughter arrives and calls the paramedics, it will only have been two hours since the grandmother first noticed her air conditioner’s grinding. “That’s part of what makes [heat stroke] so lethal,” Willamette Week wrote after the heat wave in the Pacific Northwest in 2021 killed an estimated 250 Americans: “You can go from feeling bothered by the heat to dead in 90 minutes.”

Victims of classic heat stroke are often elderly, often have pre-existing health conditions, often are socially isolated, and often are low-income. In an analysis of heat deaths in Multnomah County (where Portland, Oregon, is located) in 2021, The Washington Post found 61 percent of confirmed deaths were in areas with above-average poverty rates. In the same story, the reporters found that a “direct outreach” program in Philadelphia — which includes a “mass notification system,” “the number for a 24-hour hotline staffed by nurses [flashing] from one of the city’s tallest high rises,” and a 5,000-strong volunteer team that mobilizes “to check on high-risk neighbors” — saves an average of 45 lives per year.

If the grandmother had been younger, she might have been treated with “cold-water immersion,” which is one of the fastest and most reliable ways to address heat stroke. (Willamette Week reports Oregon paramedics resourcefully filled body bags with ice and had those suffering from heat stroke crawl inside). In the case of the elderly, though, it is advised to treat heat stroke with more easily tolerable cooling methods, like the application of ice packs and cold, wet gauze.

Either way, the outcome past the threshold of heat stroke is uncertain. As Stark, the master of the cautionary tale, writes, “A study reviewing 58 of the severe heat stroke victims [after a 1995 Chicago heat wave] found that 21 percent died in the hospital soon after admission, 28 percent died within a year, and all the remaining subjects experienced organ dysfunction and neurological impairments.”

But he sees a grim silver lining. “It could be a small measure of good fortune,” writes Stark, “that confusion, semiconsciousness, or coma overcome victims as they succumb to severe heatstroke.”

99.1 Fahrenheit

The laborer puts the nail gun down on the nearest cinderblock and sweeps the back of his hand across his brow, a portrait of I’m hot. Though the elimination of water breaks won’t go into effect until the fall, his employer has threatened to fire anyone who “slacks off” anyway, and the laborer needs this job. He watches for a moment as the heat makes strange shapes in the air above the new asphalt driveway. He thinks he might have a headache coming on.

There are five more hours to go. It’s 96 degrees out with 66% humidity.

And tomorrow will be another scorcher.