Photo: Jen Judge

what it feels like to die from heat stroke

Heatstroke kills thousands of people every year. This is what it feels like—and how to know when you’re in danger.

By Peter Stark | Outside Magazine | 2022

End of the dirt road. You brake to a stop, swing your leg over the scooter, and kick the stand into place.

The effort makes your head throb. The scooter wobbles. Your sunglasses slide down the mixture of sweat and sunscreen on your nose. You adjust them, look up tentatively at the fiery orb in the deep blue sky, and flinch. You chide yourself for staying out so late the night before, for not getting an earlier start this morning. The sun already feels too hot. But this is your only chance to surf Emerald Cove. It’s gonna be OK, you tell yourself. You’re in good shape. You’ve got the stamina to hike the five miles over the ridge and down to the beach before the tide comes in.

That glaring sun, of course, is essential for life on this planet. But its thermal energy, which we feel as heat, is a force both benevolent and cruel. The human body employs a spectrum of physiological tricks to maintain the steady internal temperature—98.6 Fahrenheit—at which it thrives. There is about eight degrees of difference between an optimal level of internal heat and the limit the body can endure. This threshold is referred to as the critical thermal maximum. Exactly when one reaches it depends on individual physiology, exertion, hydration, acclimation, and other factors. Estimates place it at an internal temperature between 105 and 107 degrees. Heat is a giver of life, but when the human body gets this hot—or hotter—­terrible things occur.

Emerald Cove is on an island off the coast of South America. You’d flown over a couple of days ago, after a trek in the mainland’s cool interior highlands. You wanted to take in those thousand-year-old stone statues you’d heard so much about, plus you figured you could cap off your vacation with a couple days of surfing. You’re just a beginner, and already you’re hooked, but it’s hard being a newbie. The locals are reluctant to let you into the lineup. What you need is that perfect undiscovered break, no people, no pressure.

Last night you walked into a popular surf bar and pulled up a stool next to two guys you’d seen in the water that day. If you wanted to find a secret spot along this spectacular wave-battered coast, you figured these guys would be the ones to know. They gave you a cursory nod and continued their conversation.

“Huevón,” one was saying to his pal (or at least that’s what you think he said). Your Spanish is OK, but you’re not catching all the slang. He was talking about a point break.

“Qué bacán!” Rad! “And there’s nobody there. Nobody. You have to try it.”

“Nobody where?” you asked quietly, leaning in.

“La Cala Esmeralda.” He barely turned his head to look at you.

“Emerald Cove?” you repeated.

It had taken a long time, a lot of patience, and too many piscolas—pisco and Cokes—to pry out where it was, but the effort was worth it. It’d be the perfect end to a perfect trip, something to talk about to your well-traveled friends back home. “Seriously, you’ve never been there?” you’ll say to them, acting surprised. “You should definitely check it out. But it’s kinda hard to get to, and the trail’s a secret.”

You had to ask the surfers to repeat themselves, just to be sure you understood. They’d finally turned and looked at you full on.

“Dude,” one said, “I’m not sure I’d try it if I were you.”

Heat-related illnesses in the U.S. claim more lives annually than hurricanes, lightning, earthquakes, tornadoes, and floods; there were over 9,000 heat-related deaths between 1979 and 2014. The fatalities tend to peak during heat waves and hotter-than-average years, and they’re expected to rise as climate change affects global temperatures. One of the deadliest heat waves in modern times swept Europe in 2003, killing over 30,000 people as temperatures soared to 100 degrees for days on end.

The human body is much less tolerant of rises in internal temperature than drops. The lowest body temperature a human has been known to survive is 56.7 degrees, nearly 42 degrees below normal. Anna Bagenholm, a 29-year-old Swedish woman, was backcountry skiing when she broke through eight inches of ice into a frozen stream. Her upper body was sucked down, leaving only her feet and skis visible, but she managed to find an air pocket and was able to breathe. After 80 minutes, she was finally rescued. Bagenholm remained in a coma for about ten days and was in intensive care for two months but ultimately suffered only minor nerve damage. On the other end of the spectrum, the highest body temperature measured was only 17 degrees above normal. Willie Jones, a 52-year-old Atlanta man, was rescued from his apartment during a heat wave in 1980. His internal temperature was 115.7. He spent 24 days in the hospital before being released.

While there is some debate, studies on women in the military have shown that they may be more susceptible to heat illness than men due to their higher body-fat content and lower sweat output. Whether the heatstroke victim is male or female, the odds of surviving depend on the duration of overheating and, once their condition is discovered, how quickly they can be cooled down—most effectively by immersion in ice water within 30 minutes. Survival, moreover, doesn’t guarantee full recovery. A powerful heat wave in Chicago in 1995 caused 739 deaths and 3,300 emergency-room visits. A study reviewing 58 of the severe heatstroke victims 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.

An average-size male at rest generates about as much heat as a 100-watt light bulb simply through metabolism. During moderate exercise, temperature increases nearly ten degrees every hour unless you cool yourself by sweating or some other means. You risk a variety of illnesses, starting with heat edema, which entails swelling of the hands and feet and can begin at body temperatures close to normal. No precise temperature marks the onset of the various other heat illnesses, and the order of symptoms varies between individuals, but they may include heat syncope (dizziness and fainting from the dilation of blood vessels), heat cramps (muscular clenching due to low salt), and heat exhaustion (identified by muscular weakness, rapid heartbeat, nausea, headache, and possible vomiting and diarrhea). Finally, an internal temperature of 105 marks the lower boundary of heatstroke territory, with outward symptoms of extreme irritability, delirium, and convulsion. Because of individual variation in how these symptoms appear, and because some may not appear at all, athletes in particular can be overcome quickly and with little warning.

There are two kinds of heatstroke: classic and exertional. Classic heatstroke hits the very young, the elderly, the overweight, and people suffering from chronic conditions like uncontrolled diabetes, hypertension, and cardiovascular disease. Alcohol and certain medications (diuretics, tricyclic antidepressants, antipsychotics, and some cold and allergy remedies) can increase susceptibility as well. Classic heatstroke can strike in the quiet of upper-floor apartments with no air-conditioning.

Exertional heatstroke, on the other hand, pounces on the young and fit. Exercise drastically accelerates temperature rise. Marathon runners, cyclists, and other athletes sometimes push into what used to be known as the fever of exercise and is now called exercise-induced hyperthermia, where internal temperatures typically hit 100 to 104 degrees. Usually, there’s no lasting damage. But as body temperature climbs higher, the physiological response becomes more dramatic and the complications more profound. The higher temperature can ultimately trigger a cascading disaster of events as the metabolism, like a runaway nuclear reactor, races so fast and so hot that the body can’t cool itself down. A person careens toward organ failure, brain damage, and death.

It’s February, the height of summer in the Southern Hemisphere. You’d planned to get up early but didn’t hear your alarm after the late night at the bar. Now the sun is well into its arc. The temperature is supposed to hit 93 degrees by midday.

Pulling the keys from your scooter, you sling your rented surfboard onto your back, thread your arms through your chest pack, and hear the reassuring slosh of the water bottle inside. You have a seat on the twice-weekly plane that leaves tomorrow, returning you to the mainland. If you’re going to do this, the moment is now. You launch up the trail, a faint unmarked path on the gentle, grassy slope. You’re not surprised you’re the only one around. The surfers said to follow the volcano’s right flank until you gain the ridge, then drop down a cleft in the rocks to the sea. Good luck finding the cleft, they seemed to say. Maybe they were just trying to deter you. You see the slope steepen as it rises toward the sharp crest, where chunks of volcanic rock protrude like broken dinosaur scales through velvety green nap. No trees, not a wisp of wind. Ancient cultures deforested this island centuries ago and mysteriously disappeared, leaving not a sliver of shade under the tropical sun.

You feel the quick flex of your quads, the push of your glutes, the spring of your calves propelling you up the winding path, and hear the steady mantra of your breathing. You have to make time. The guys at the bar said the shore bristles with stone dientes, teeth—get there at low tide. That gives you just under two hours.

Within only a few steps, your body begins to respond to the sun’s radiation, the moist air pressing against your skin, and the heat generated by your own rising metabolism. Blood coursing through your arteries begins to grow warmer. At less than one degree Fahrenheit above your normal internal temperature, receptors in your brain’s hypothalamus start to fire, signaling the circulatory system to shunt more blood toward your skin’s surface for cooling. Other messages tell peripheral blood vessels to dilate, opening up to allow greater blood flow. Still other signals activate millions of tiny coils and tubes embedded in your skin—your sweat glands. Concentrated within your head, palms, soles, and trunk, the glands pump water from a tiny reservoir at the base, pushing the salty liquid up a long tube through layers of skin to erupt in a miniature gusher at the surface.

Several hundred yards up the grassy slope, sweat is popping onto your face. You feel the slick, dark blue fabric of your shirt sticking to your back, despite its breathability. You wish it was looser, and a lighter color that didn’t so readily absorb the sun’s rays. A trickle of sweat runs down your forehead and into one eye, stinging with dissolved salts, blurring your vision.

To be continued….

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