How to Prevent Hypothermia While Hiking and Backpacking
By Michael Lanza
Rain and wind battered two friends and I as we hiked across exposed meadows high in the Olympic Mountains—our second straight day of rain. Dripping, knee-high vegetation ladled cups of water onto our pants and boots. My rain jacket kept my upper body dry, but my soft-shell pants eventually soaked through. That, and the wind, slowly made me steadily colder—more than I realized.
After a strenuous ascent of a steep mountainside, carrying a heavy pack with my jacket hood up—which should have made me quite warm—it occurred to me: I’m still cold.
I was hypothermic.
What’s more, we had all—ironically, given the rain—run out of water more than an hour earlier. We undoubtedly hadn’t eaten enough to replace the calories burned through a full day of hard hiking in cold wind and rain. Now, as the rain continued pounding us, night approached and we were nowhere near a water source or flat ground for camping.
We understood that our situation was serious. We calmly discussed our priorities. First and foremost, we needed a spot to pitch our tents—under the circumstances, shelter was more important than water, because we knew we could survive a night without water and that we’d find some in the morning, and we had plenty of food. But a night without shelter in those conditions posed far greater risks.
We backtracked to a flat area we had recalled passing earlier, and spent the night dry and warm in our tents, although without water. The rain had stopped before we set up camp, and clear skies greeted us the next morning. Two hours after leaving that camp, we reached a creek and drank copiously. We had gone about 20 hours without water, but hadn’t felt any serious effects from dehydration. Prioritizing shelter and warmth had been the right call. And I was amazed at how juicy dried mangoes taste when you have a raging thirst.
If you’ve spent much time outside in wet, cool, or cold weather, you’ve probably been at least mildly hypothermic. Most likely, it wasn’t serious and you easily remedied the situation with clothing, food, or shelter, or by descending out of the wind.
But hypothermia isn’t like an ankle sprain, occurring suddenly and broadcasting its symptoms clearly. And it isn’t like hunger, always remedied with a quick fix. It can happen quickly, or it can sneak up on you slowly. It may happen even when you believe you’re dressed well, because you didn’t initially feel cold. While it’s an obvious threat in the dead of frigid winter, it happens perhaps more often on cool, windy days in spring and fall, and certainly can happen in the mountains in summer.
Hypothermia can present a minor obstacle if recognized and addressed soon, or escalate into an emergency and even prove fatal.
Plus, as those two friends and I—all very experienced backpackers (and two of us experienced climbers) who’ve endured severe weather numerous times—discovered that day in the Olympics, it can happen to anyone.
In this article, I’ll explain what hypothermia is and how it happens, and offer expert tips and skills on how to avoid hypothermia and treat it when it happens to you or a companion, drawn from more than three decades of wandering through the backcountry in all kinds of weather, all over the U.S. and the world (and shivering more times than I could estimate).
Trust me when I say this: Someday, you will use these tips.
Please share your own trips, tricks, or thoughts in the comments section at the bottom of this story.
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Hypothermia is defined as a core body temperature of 95° F/35° C or lower, which is about three degrees Fahrenheit below the average normal body temp of 98.2° F/36.8° C (although “normal” can vary from 97° to 99° F between individuals). Hypothermia occurs when someone is losing body heat faster than she can produce it, causing the body’s core temperature to drop.
While it’s hard to find statistics on how many hikers die from hypothermia, according to the Centers for Disease Control, an average of 1,300 Americans die from hypothermia every year. While most of those victims are undoubtedly nowhere near the backcountry, according to the National Park Service (reported in this Washington Post story), “cold exposure” accounted for about 25 deaths in all national parks between 2003 and 2007. That’s actually far fewer than deaths from falls (about 175), vehicle accidents (over 250), and drownings (over 350).
Still, hypothermia poses a significant risk to backpackers, dayhikers, climbers, and others in the backcountry. Preventing it begins with knowing how to recognize it.
How to Recognize Hypothermia
Mild hypothermia, or the onset of hypothermia, isn’t always obvious; you have to pay close attention to recognize it in yourself or companions, especially when it comes on gradually. As with my experience in the Olympics, it can progress slowly just from hiking wet in cold rain and wind, or skiing without quite enough clothing, or failing to add a needed layer as the temperature slowly drops.
But it’s critical to recognize it early, when it’s easier to address and fix quickly.
Advanced hypothermia, on the other hand, is very obvious—the victim is, at the least, probably shivering violently, and losing consciousness as it worsens. But by then, the situation is grave, not easily or quickly remedied, and can be fatal.
Symptoms of the onset of hypothermia include:
• Diminished dexterity in fingers
• Slurred speech
• Compromised balance and coordination and slower physical responses
• Confusion and poor judgment
Symptoms of advanced hypothermia include:
• Impaired and steadily diminishing consciousness
• Shivering, followed in extreme hypothermia by the cessation of shivering
• Skin growing increasingly pale
• Shallow breathing
• Weak or irregular pulse
• Dilated pupils
• Muscle rigidity
Never get cold again (well, almost never). See my “5 Tips For Staying Warm and Dry While Hiking”
and “10 Tips for a Smarter Layering System.”
How to Prevent Hypothermia
Whether a group of experienced hikers, backpackers, or climbers, or a young family on a dayhike, the strategies for identifying and preventing or dealing with hypothermia are the same. The following tips will help you avoid it—which is always much easier than treating hypothermia.
Know the Forecast. Most multi-day backcountry trips (and certainly dayhikes) are short enough that you can get an accurate long-range forecast for daytime and nighttime temperatures, precipitation, and wind. Remember that temperatures drop about three to five degrees Fahrenheit with every 1,000 feet of elevation gain, and winds can increase exponentially.
Watch the Weather. Monitor changes in weather throughout the day—it may not play out according to the forecast—and adjust your clothing and plans accordingly. Be open to the idea that you might have to change or abort your original plan.
Watch for Early Signs of Hypothermia. Early indicators of core body temp slipping downward include cold fingers and toes or slight difficulty speaking clearly. In wet or cold weather or wind, ask young kids frequently if they’re warm enough, and specifically how their fingers and toes are feeling.
Watch kids or adults for signals like a hunched posture (think how you naturally draw arms and shoulders in when cold), looking tired, apathy, slowing down, getting grumpy, or talking less than normal. Get the right clothing on them quickly, because the sooner you head off hypothermia, the faster someone returns to a normal temperature. Waiting to add a needed layer prolongs the time it takes for someone to rewarm.
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Bring the Right Clothing. A versatile layering system that keeps you comfortable in a wide range of conditions includes:
• Synthetic or wool base layers that wick moisture and dry quickly rather than retaining moisture from perspiration.
• Adequate insulation for the potential temperatures and conditions.
• A shell jacket that keeps you dry and blocks wind.
For outings of several hours or multiple days in inclement weather, your jacket, especially, should be waterproof and breathable to keep precipitation and wind out and release moisture that your body produces. I’ll wear soft-shell pants in foul weather for their superior breathability, because waterproof-breathable rain pants can cause you to overheat; but the latter may be necessary in very wet and cool (but still above-freezing) conditions.
I commonly find that, for my body, wearing just a shell jacket over a midweight, long-sleeve base layer—and no middle layers—when hiking in moderate temps (40s to 50s Fahrenheit) gives me the needed protection from wind and precipitation without causing me to overheat. But people have different cold tolerances. Experiment with adjusting layers in different conditions; in time, you’ll adjust less often because you’ll know what your body needs for layers across many situations.
Stay dry, happy, and safe. See my picks for “The 5 Best Rain Jackets For Hiking and Backpacking.”
Warm Up by Moving. Clothes offer only insulation and protection from the elements; your body produces heat, and it does that best through movement. When you feel cold, start hiking again. In cold temps and wind, take brief rest stops to avoid cooling down rapidly.
Anticipate the Wind. Strong winds do not materialize out of thin air—they blow consistently through and around certain terrain features because of the topography of mountains and canyons and the nature of weather and air movement.
Mountain passes, notches, and summits and canyon rims are like the small end of a funnel—where rivers of wind get squeezed through confined spaces or unleashed after rushing up large elevation gradients—so powerful gusts often inhabit these features even when the air is calm below them. Use these simple strategies:
• Put on a shell and extra insulation, gloves, and hat if needed right before you reach these places (you’ll be able to see or hear if it’s blowing hard right before reaching, say, a mountain pass).
• Read the wind direction and take shelter in the lee of cliffs and ridges when needed.
Which puffy should you buy? See my “Review: The 10 Best Down Jackets” and
“Ask Me: How Can You Tell How Warm a Down Jacket Is?”
Worship the Sun. Besides the air temperature dropping as you gain elevation, the sun’s heat can also feel more intense as the amount of atmosphere above you gets thinner. That can be helpful, but it also creates a growing dichotomy in how warm you’ll feel in sunshine versus in shade, which gets only amplified by wind. Be aware of it and adjust layers accordingly if you’ll be in sun or shade for long enough to affect your comfort.
Minimize Sweating. We all can break into a glorious sweat on a long uphill climb, especially when carrying a heavy pack. But as much as possible, minimize how wet your base layers get before reaching higher elevations and mountain passes that may suddenly grow substantially colder and windier. Use these strategies:
• Peel off layers for the ascent.
• Pace yourself to avoid getting soaked, and if necessary, dial back your pace just before reaching the top, to start drying out your base layer top.
• If needed, change into a dry and warmer top before entering a sustained windy and colder stretch of hiking. Or wear a waterproof-breathable jacket over a damp shirt to help you dry that shirt more quickly with body heat (as long as the wet shirt isn’t making you too cold to produce heat).
• When possible, time long uphill stretches for cooler times of day, like early morning, when you won’t sweat nearly as much.
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Eat and Drink. Your body temp can sink simply because you’re not ingesting enough fuel to replace the calories you’re burning, or because you’re dehydrated—which can occur even in cold temps, when you may not be sweating. By the time you feel depleted, hungry, thirsty, or tired, your body has probably already run low on fuel and fluids.
• In cool or wet conditions, snack regularly throughout the day, especially on high-fat foods (chocolate, nuts, cheese, peanut butter—whatever everyone likes). Children need snacks more frequently because they lack the fat reserves of adults.
• Better to drink frequently than guzzle randomly, because the body can absorb no more than about a liter of water an hour.
• When stopping at a water source to refill, drink plenty and snack, following the rule that it’s better to carry water in your belly than on your back.
• When sleeping outside in cold temps, eat foods high in fat and protein before bed; those slow-burning energy sources keep you warmer through the night.
Know Escape Routes. When heading out in mountainous terrain where you may be exposed to wind and wet weather for an extended period of time, know your options for trails and routes you can take to descend quickly to more-protected terrain and warmer temperatures. Before setting out across a long stretch with no good descent options, reassess everyone’s condition to confirm your entire party has good energy levels and feels adequately warm to continue; if not, retreat.
You don’t have to be cold at night. See my “10 Pro Tips For Staying Warm in a Sleeping Bag.”
How to Treat Hypothermia
In an extreme scenario, a hypothermia victim may not get warm just by moving, putting on more clothing, eating, and drinking warm fluids. That can occur quickly—as when someone falls into a frigid river—but more commonly comes on slowly. When someone exhibits symptoms of advanced hypothermia, you must quickly get that person to a place sheltered from wind and precipitation and insulate her as much as possible.
If you have a tent, pitch it (preferably in a good, protected campsite, just in case you have to stay there for a while) and get the victim into a sleeping bag on an insulated pad or air mattress. If you don’t have a pad, use an empty backpack, a removable back pad from a pack, or anything similar that will insulate the victim from the ground; piling leaves below the victim is even better than direct contact with cold ground.
If you don’t have a tent, get to the best protected terrain you can reach quickly and get the victim out of any wet clothing and into all available insulation layers, with shell outerwear that blocks wind and precipitation.
The bodies of children and some adults may still not rewarm very fast. Try having one or two people huddle or lie down with the victim (one person on each side) to share body warmth. If you’re in a tent or sheltered from the weather, cover yourselves with an extra sleeping bag opened up.
Be safe by hiking smarter. See my “7 Pro Tips For Keeping Your Backpacking Gear Dry.”
Give the victim food and hot drinks if she’s able to ingest them on her own. You may have to make a judgment about when or whether that person can continue under her own power; if she has the energy to do it, walking can help her get warm again. But moving someone too soon may be the worst option if she’s so cold that it affects her physical functioning—look for symptoms like badly slurred speech and stumbling—so be prepared to spend the night and find an appropriate place to do that.
Thanks for reading this entire article. I hope your big takeaway from it is that the smartest strategy is simple and easy: avoid hypothermia.
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