Travis Olander 08.08.24
Extreme heat is increasingly breaking records across the globe — especially here in the U.S. In the midst of summer 2024, most Americans have experienced at least one extreme heat event: Periods of potentially fatal temperatures above 90 degrees Fahrenheit lasting for at least 48 to 72 hours. Heatwaves are here to stay. They’re not just increasingly common, either. They’re increasingly omnipotent, affecting broader swathes of the country, including historically mild climates. These crushing heat domes are now more often found hovering, sometimes for weeks on end, atop some of the most trafficked outdoor recreational hotspots (pun intended).
Heatwaves can KILL in Minutes
These heatwaves can do far more rapid harm to your life expectancy than you might think, too. Just weeks ago, two experienced hikers succumbed to triple-digit heat in Canyonlands National Park, Utah. They ran out of water during what was supposed to be a mild daytime hike and, just after dialing 911 but before rescuers promptly reached their known location, the 52- and 23-year-old father and daughter perished.
That these temperatures can kill you in minutes is not hyperbole. Studies have shown that when outside temperatures are above 90 degrees (F), your body’s core internal temperature can climb to fatal numbers — above 104 degrees (F) — in as little as 10 to 20 minutes.
The mechanism for this rise in body temperature is caused by dehydration. Your body sweats to shed heat, releasing water through the skin that evaporates to cool you off. But the more you sweat, the more water you lose. The higher the outside temperatures, the quicker dehydration sets in.
It’s Simple: Drink to Survive
Once dehydration reaches severity, you’ll experience heatstroke: A runaway internal body temperature that can literally cook your organs and lead to a heart attack.
Obviously, re-hydration is the key to surviving these extreme temperatures when you’re recreating outdoors. “Drink–water!” Was the command uttered in a cadence rhythm and drilled into our heads every 15 minutes during 100-degree ruck marches through the flat, hot Hell of Ft. Sill, Oklahoma. But how much water do you really need? Is plain ole’ agua really the best way to stave off shriveling death? No, but we’ll get to that.
When you’re intensely recreating outdoors during extreme heat events, you can sweat between 1 and 3 liters of water per hour — that’s up to nearly 6 pounds of fluid. One study showed that symptoms of dehydration can start when you lose just 1% of your body weight in water, with dehydration becoming life-threatening at 10%.
For a 180-pound male, that means you’re dehydrated after losing about 1.8 liters of water, which can happen in under an hour, and you’re on death’s door once you lose 18 liters. In other words, going just a few hours without replenishment can be enough to induce a long dirt nap.
You need to Drink at LEAST as much Fluid as you Sweat
Pretty simple: You need to replace the fluids you sweat. Think of it like re-filling a leaky radiator. Once the radiator runs dry, overheating occurs. At a minimum, you should consume one cup (about a quarter liter) of liquid every hour, and take action to reduce the amount of sweat your body must produce to cool itself.
When you’re in the sticks enjoying that hot, dry hike through your favorite national park, pace yourself and take frequent breaks — in shade, whenever possible — to reduce fluid loss to sweat. Avoiding direct exposure to the sun by wearing hot-weather, long-sleeve clothing, a good sun hat, ventilated boots or shoes, and a neck cover are all potential lifesavers.
Water alone can be Dangerous – You must Restore Electrolytes
The word “fluid,” not “water,” needs emphasis. Drinking nothing but water is a sure way to introduce myriad other health problems when you’re re-hydrating. That’s because when you sweat, you’re not just losing water. You’re losing critical vitamins and minerals that regulate the function of your organs and nervous system.
Water intoxication is a very real emergency caused by diluting your body’s electrolytes, frequently the result of drinking excessive amounts of water due to dehydration. When too much sodium, in particular, is lost, confusion and nausea can set in. Vomiting exacerbates dehydration and, in the worst cases, too much lost sodium can cause an irregular heartbeat, confusion, seizures, and death.
Electrolyte powders are the simple solution. They contain calcium, phosphorus, magnesium, chloride, sodium, potassium, and all the other electrolytes you lose — and then further dilute — from sweating and re-hydrating with water.
To keep topped up on the bare minimum electrolytes, follow these basic guidelines by adding the following to one liter of water:
- 2.6 g of sodium chloride
- 1.5 g of potassium chloride
- 2.9 g of sodium citrate
- 13.5 g of glucose
When Humidity’s High, Keep Activities Short n’ Simple
High humidity can negate your body’s ability to self-regulate its internal core temperature through sweating by inhibiting the evaporation of sweat itself. Researchers found that when humidity is 100%, a temperature as low as 87 degrees (F) is enough to inhibit sweat evaporation, effectively smothering your body’s natural radiator and greatly increasing the chances of suffering heatstroke.
When temperatures are even higher, lower humidity can still inhibit the ability cool through sweating. Other studies have shown that a humidity level of just 50% at 115 degrees (F) is enough to cause problems — in this case, no amount of hydration will be sufficient to avoid heatstroke, because the act of sweating won’t actually cool you off.
In these conditions, keep your activities outdoors more limited in duration. You wouldn’t spend three hours sitting in a sauna, and you probably shouldn’t expose yourself to the same whilst scrambling along your local trails.
Speaking of liters of fluid…
Above all else, you need a reliable, small, compact day pack to carry enough water (and electrolytes!) during these extreme heat events. Check out our review of the Mystery Ranch Rip Ruck 15. It’s the perfect day-hike backpack: Enough capacity to carry some bottles and a Camelbak, without feeling bulky.
