Why Extreme Heat is Nature’s Stealthiest Killer

As temperatures worldwide continue to soar, it's time to understand the insidious danger of extreme heat.

Photo: Photo by Mario Tama/Getty Images

Heading out the door? Read this article on the new Outside+ app available now on iOS devices for members! Download the app.

Out Alive is a podcast about real people who survived the unsurvivable. Check out more seasons and episodes here.

When we anticipate encountering bears, we come equipped with bear spray and knowledge of how to act. In avalanche terrain, we know to pack our beacon, shovel, and probe. Yet we tend to overestimate the danger of a bear attack. But when it comes to the most deadly natural hazard, heat, our readiness often wavers. Why do we consistently underestimate such a palpable threat, and what are the cognitive mechanisms at play? In this deep-dive episode, Dr. Peter Howe’s groundbreaking research reveals a startling truth. Join us as we venture into one of the hottest places on earth, Death Valley National Park. Our special guests, a climate researcher and a seasoned representative from the park, offer life-saving advice on navigating and staying safe in extreme heat conditions. The temperatures are rising, and our awareness should be, too.

If you want to know more about steps we can do as individuals head to our column, Climate-Neutralish. There are tons of great suggestions there for small habits we change that make a big difference.


Louisa: The headlines this summer have been undeniably bleak when it comes to the death toll surrounding hikers and the extreme heat. Two women were found in Valley of Fire State Park: Jessica Rhodes, age 34, a regular at her local gym and athlete and her companion, 29-year-old Diana Rivera. Both women were medical professionals.

Rhodes was found a quarter-mile away from her car. In another incident earlier this summer at Big Bend National Park, a stepfather was hiking with his two stepsons, ages 14 and 21. They all lived in Orlando, Florida, so not unaccustomed to heat, but perhaps misjudged the strenuous 14-mile loop, where summer temperatures often exceed 110 degrees Fahrenheit, and there is no shade or water.

The 14-year-old showed signs of illness, eventually losing consciousness. His stepfather left the boys and went back to their vehicle to drive for help. After park rangers found the body of the 14-year-old, the father was also found dead in their camper van, which had been driven over an embankment just a few hundred feet from the trailhead.

Authorities suspect he succumbed to heat-related illness. There were also two separate deaths at Death Valley National Park last month. Here’s Nichole Andler from Death Valley. She’s their chief of interpretation and education. 

Nichole Andler: During the month of July, there were two fatalities at Death Valley. Both of which likely had some relation to the extreme heat. There was one gentleman who drove off the road and the vehicle stopped. There was no crash, but they had their windows down and their AC on their vehicle appeared to be inoperable, and the overnight lows that night were 96, and so the high temperatures during the day, it got up to 126, so most likely heat was a factor in their death.

Louisa: According to a report from the Park Service, the victim here was a 65-year-old man from Southern California. His car was 30 yards from the road, and he was not stuck. 

Nichole Andler: Another gentleman, Steve Curry, he was someone who came to Death Valley fairly often. He was an avid outdoorsman. He knew what to do to prepare for heat. He was wearing his sunscreen. He had a hat on, he had water. He was wearing long sleeve, loose fitting clothing to help. You know, just did everything right, checked all of the boxes, but even though he was prepared, it still resulted in a tragic ending to his hike.

Louisa: Curry collapsed outside the restrooms at the trailhead where his car was parked after completing his 2-mile hike. Taking a closer look at the latest heat-related fatalities together, we noticed that the victims spanned in age and many of these tragedies occurred when help was agonizingly close. What is it that sets extreme heat apart from other natural dangers? According to a 2019 study, it may be that we simply underestimate the risks of heat exposure.

Dr. Peter Howe: My name is Peter Howe. I’m a professor in the Department of Environment and Society at Utah State University here in Logan, Utah, and my research focuses on how people perceive and respond to environmental risks, in particular risks related to climate change. In the context of heat, we know from a scientific perspective that heat is the deadliest natural hazard in the United States, so it causes more deaths every year than floods or tornadoes or wildfires or hurricanes, but it’s not a hazard that people necessarily perceive to be as great of a risk as it actually is.

Louisa: Not only do some hikers underestimate the risks of extreme temperatures, they actually seek them out. Death Valley National Park, which boasts the hottest place on earth, is seeing an increase in visitors this year from previous years, and the heat is the point for some visitors wanting to experience the temperatures as a bucket-list opportunity. According to an article in the Wall Street Journal, as temperatures continued to break records, cars lined up with visitors waiting to take their selfie with the parked giant metal thermometer. 

Dr. Peter Howe: And so this phenomenon of heat tourism is somewhat concerning. On the one hand, if we have people who are visiting places specifically to experience heat, when we know that many people don’t necessarily appreciate the magnitude of the risk that extreme heat causes, heat is a tricky hazard for us as humans to really appreciate. It’s not very visible in comparison to a flood or a wildfire. It doesn’t necessarily attract a lot of media attention, partly because it’s not particularly visible. It’s something that once it’s over, it’s a little bit hard to recollect unless the impacts on you are very severe. 

Louisa: Just as we meticulously prepare for high-stake adventures like multi-pitch climbs or lengthy solo treks, we must apply the same rigor of preparedness every time we arrive at the trailhead. The wilderness demands respect, whether it’s a challenging summit or a simple afternoon hike. 

Nichole Andler: We see during the summer months folks who are coming to experience the heat. When someone decides that they want to come and visit their national parks for whatever reason, then of course we want them to come and enjoy these places, but we really want them to be safe.

If you think that you want to do one of our shorter hikes—we don’t recommend long adventures—if you’re gonna do one of our shorter hikes, figure out how long the hike is itself, how long that typically takes you. Build in a little extra time, and bring enough water to get you through that. We recommend 4 liters per person per day while you’re visiting here, but some folks will need a little more.

We also recommend salty snacks, so things like chips, pretzels, bacon, whatever helps to replenish some of those minerals to your body. And while water is probably one of the best things you can drink, mixing in a little bit of something else like orange juice or electrolytes is also good.

Louisa: Even if you’re prepared for a hot day, you still may not be assessing the danger accurately. Dr. Howe’s research shows that we have a really hard time judging the hazard of heat, even when conditions are extreme. 

Dr. Peter Howe: I was working with a graduate student on a project related to her thesis that we published a paper studying the risk perceptions of heat among hikers in southeastern Utah at Arches National Park and the surrounding area. And from her study, we found that people actually didn’t necessarily perceive the risks of heat to be worse when the temperatures were hotter than we measured.

And that’s one of the more concerning findings out of that study. You might expect people to think that the risks themselves would be greater when it was hotter out, and then they might therefore take more protective actions like carrying more water, maybe not taking as long of a hike. But we didn’t see that.

Louisa: Dr. Howe explained that this tracks with what he’s seen on a national scale. We tend not to believe the risks to be worse even when we fall within a vulnerable demographic. For example, the elderly or more at risk for heat illness, but his research does not show that older people tend to perceive that their risk is much higher. But understanding these perceptions and biases is the first step to changing. Dr. Howe hopes that this research will allow us to share focused information. 

Dr. Peter Howe: I think one thing that we need to emphasize is that everybody is at risk of heat. Even if you’re not in one of those categories that tends to experience more health risks, everyone is susceptible to experiencing health impacts. So, we all need to remember to take precautions when we’re out in hot weather. Heat is a risk for everybody and it is relatively less visible, but an extremely deadly hazard. In fact, the deadliest natural hazard in the U.S. I would also point out that it’s also something that we can all contribute to reducing the risks of. Vote for pro-climate policies and take actions on the individual level that will reduce the risks in the future.

Louisa: If you want to know more about steps we can take as individuals, head on over to outsideonline.com and check out the column “Climate Neutral-ish.” That’s “Climate Neutral-ish.” There are tons of great suggestions there for small habits we can change that make a big difference.

This episode of Out Alive was produced and written by me, Louisa Albanese with writing and editing by Zoe Gates. Sound Design and Mixing was by Jason Patton. Thank you to Dr. Peter Howe and Nicole Andler for sharing your time, stories, and perspectives with us. If you have a story you’d like to share, on Out Alive, you can email me at outalive@outsideinc.com.

From 2022