Hot

2025, Winter Adirondac Adirondoc

On a warm summer’s day in 2021, a young family living near California’s Sierra Nevada Mountains parked their truck and began a day hike. They were never seen alive again.

When the family was reported missing by friends, a massive search began. Not long afterward, their bodies were discovered near a trail. The father, young daughter, and dog were peacefully seated; the mother was a bit further away, apparently attempting to scramble up a hillside. There was no evidence of foul play.

The tragic discovery set off a flurry of speculation. There were a number of old mines nearby; could there have been a sudden discharge of poisonous gas? Toxic algae had been noticed in some nearby water sources; could they have been poisoned? Carbon monoxide? Snakebite? Online commentaries entertained even more exotic explanations.

After extensive scene investigations and autopsies, including of the dog, officials announced the cause of death. High environmental temperatures, combined with exertion and limited water intake, had resulted in severe heat stroke.

Sadly, this tragic experience has not been unique recently. A healthy 30-year-old woman succumbed to heat while hiking in Utah’s Snow Canyon State Park this past July. A few days before, a father and daughter died from the same thing in Canyonlands National Park in Utah. The previous July, a 57-year-old woman died from heat stroke while hiking in Grand Canyon National Park.

None of these folks had serious underlying illnesses. None were practicing “extreme” sports in challenging environments. All were on day hikes in areas frequented by travelers.

Because there is no registry of such deaths, exact numbers are impossible to ascertain. There were at least seventy- seven heat-related deaths in national parks between 2007 and 2023. News reports of such deaths are frequent. One thing is quite clear: this is a relatively new phenomenon.

These catastrophes have caused me to redo my teaching on heat problems in my wilderness first aid classes. For years, I taught that ”heat exhaustion” was simply dehydration occurring in a hot environment. It could be treated by rest, cooling, and fluids. That is still correct. “Heat stroke,” the more serious heat illness, was mainly restricted to extremes of activity or environment, or to the elderly or chronically ill. It was not an issue for the typical user of the wilderness.

I was wrong. We need to revisit this topic.

Basically, human life involves the continuous, simultaneous operation of a number of chemical reactions. As for any chemical reaction, these work only in a narrow range of temperatures. In order to maintain temperature in this range, the body has mechanisms to dissipate heat. Evaporation of sweat from the skin produces cooling. Radiation of body heat to the outside occurs with increased blood flow. to the skin.

When the outside temperature is higher than that of the body, radiation is limited or absent. When environmental humidity is also high, evaporation ceases. Thus, even for healthy persons, remaining in an environment of high heat and humidity eventually causes the body to overheat. If the temperature is significantly above that of the body (say, 110 degrees or above), decompensation occurs rapidly. Once the core body temperature is consistently above 105 to 107 degrees, blood flow to vital organs slows and failure of most organs occurs. Once this is established, death is almost inevitable.

When a patient with heat stroke is encountered, they will have dry, red skin and feel warm to the touch. There will be impaired consciousness, and shock will likely be present. Once the airway is secured, the only possible field treatment is external cooling. Unfortunately, options for this in the wilderness are quite limited. Providing shade and, if possible, soaking the patient in water are about all that is possible. Emergency medical services teams in cities with a high frequency of heat illness actually utilize body bags filled with ice. Unless immediate evacuation to hospital care is available, the chance of survival is nil.

There are plenty of ways in which one can stay warm in extremely cold environments. The opposite, unfortunately, is not true. Until someone develops a backpackable air conditioner, there is simply no way in which humans can survive long-term exposure to high heat and humidity. Hydration is obviously important to maintain blood pressure and the ability to sweat, but ultimately the benefits of sweating are lost in humid environments.

The only “prevention” is avoidance. We are beginning to learn that even a hike of a few hours in high temperatures and humidity may be fatal. A reasonable guideline is to look for the predicted “heat index”; an index of 105 degrees or above should preclude outdoor recreation. (A “wet bulb” temperature of over 95 degrees is similarly dangerous, although this measurement is not as readily available.)

Finally, why is this happening now? The same reason we are seeing “new” infectious diseases in the continental United States. Climate change. Heat already claims more lives than any weather-related event. Unless we do something about it soon, we have only begun to see the painful consequences. (For further reading on this topic, I recommend Jeff Goodell’s new book, The Heat Will Kill You First. Despite the dramatic title, this deeply researched book is on my best environmental books of the decade list.)

Tom Welch, MD, is a physician at Upstate Medical University in Syracuse and an active member of the Wilderness Medical Society. He is a licensed professional guide, and a certifying instructor for the Wilderness Education Association, and has guided groups in the Adirondacks, Montana, and Alaska. More information is available at his website and blog, adirondoc.com.

Download PDF