How do you protect against hypothermia? A polar researcher shares her tips.
In subzero winds, hypothermia announces itself in small, easy-to-miss ways. Here’s what one Nat Geo Explorer does to combat it in some of the coldest places on Earth.
Blink, and your eyelashes freeze together. Exhale, and your breath turns to ice crystals. Expose any part of your skin, and it's instantly threatened by frostbite.
National Geographic Explorer Esther Horvath has stood in these conditions for hours at a time, documenting science at the very edge of human endurance.
Her work as a world-renowned, award-winning photographer has taken her across the Western Arctic, Canada, Greenland, Alaska, Antarctica, and on expeditions near the North Pole. It has included multi-month polar assignments where she has navigated drifting sea ice, crossed frigid Arctic waters, climbed snow-covered terrain, worked alongside armed spotters watching for polar bears, and endured wind chills and temperatures plunging to –55°F.
In environments like these, hypothermia isn’t an abstract medical concept. It's an ever-present life-threatening risk that must be prevented, recognized early, and managed with precision.
But you don’t have to traverse polar ice caps for hypothermia to matter. Every year, more than a thousand hypothermia-related deaths occur in the United States alone—some cases developing through events as seemingly benign as a boating accident, a stalled car, a power outage, a winter hike, or even prolonged exposure to cold rain.
By understanding how Horvath identifies and guards against hypothermia in the world’s harshest conditions, we learn practical lessons that can be applied to everyday life.
What is hypothermia?
Hypothermia occurs when the body’s core temperature falls below 95°F, or 35°C—a temperature where it loses heat faster than it can produce it. When this happens, blood vessels constrict to preserve warmth around vital organs, reducing blood flow to the skin and extremities. As circulation slows, heat can also be drained away from the core, judgment becomes impaired, and physical coordination weakens.
(What's the average human body temperature—and is it cooling down?)
And the colder the environment and the longer the exposure, the faster hypothermia develops. “Even perspiration can cause hypothermia when temperatures are low enough,” Horvath says. “The cold can make your sweat freeze against your skin.”
But one of the most dangerous misconceptions is that hypothermia only happens in extreme cold. In reality, it can occur anytime the body cannot maintain its core temperature. Strong winds, rain, poor nutrition, dehydration, and inadequate clothing can all cause it to occur—even when temperatures are above freezing.
The elderly, babies and toddlers, people who drink, the homeless, and people with hypothyrodim or circulatory conditions are especially vulnerable.
How to spot the signs of hypothermia?
In the field, Horvath watches her team members closely while also monitoring environmental conditions. “One of the first signs you pay attention to is shivering,” she explains, which occurs as the body tries to warm itself up by generating heat through increased muscle activity.
As hypothermia progresses, coordination falters and confusion sets in. “The person starts saying strange things and stops talking clearly,” she says. Making matters worse, in such a state, research shows that judgment and decision-making also become unreliable.
Eventually, exhaustion takes over as the brain misinterprets signals and creates a false sense of comfort. “You become extremely tired and just want to sleep,” Horvath says. "This is one of the most dangerous signs to look out for.”
Indeed, once someone falls asleep in a hypothermic state, their organs start shutting down as the body can no longer regulate temperature or maintain vital functions effectively. This can also cause the heart, brain, and other organs to suffer from inadequate oxygen and circulation. “At that point, you’re close to death and you can decline quickly if you don’t receive help,” she says.
And while frostbite is often associated with hypothermia as well, Horvath emphasizes that they are different. Frostbite is localized damage to skin and tissue, while hypothermia is a whole-body emergency. “You can be covered everywhere and protected from frostbite but still get hypothermia,” she explains.
How do you treat hypothermia
Horvath’s first response to the earliest signs of hypothermia is to increase movement. “We start by moving our arms and legs and by gently moving around,” she says. This helps increase circulation and generates more body heat. “But if the shivering is not stopping,” she stresses, “it’s very important to bring that person to a warm place.”
At the same time, depending on the stage of hypothermia, warming must be done slowly and carefully. In cases of severe hyperthoermia, “cannot warm the person too quickly,” she explains. This is because rapid warming can shock the heart as cold blood suddenly rushes back to the core or cause dangerous drops in blood pressure that disrupt heart rhythm.
It’s also important to be mindful about how you provide food and drink to someone experiencing hypothermia. “A hot drink or hot food heats the body too quickly,” she says. “Room-temperature water or a lukewarm beverage is usually enough initially, before providing warmer and then hotter liquids later.”
Warming up also means improving environmental conditions as quickly as possible. This includes blocking the wind, getting out of wet clothing, adding dry layers or blankets, and sometimes using skin-to-skin contact to share body heat.
Medical evaluation is also often necessary. “On the expeditions I work on, there is always a doctor,” Horvath says. “If hypothermia is suspected, we immediately inform them so they can check vitals and recommend treatment.”
How to prevent hypothermia
But for she and her team, prevention is prioritized over treatment. This starts with choosing the right clothing. “In my work, I wear only merino wool,” Horvath says. “I don’t wear cotton or typical sports materials, because cotton absorbs moisture and loses all warmth when wet, but the crimped fibers of wool trap insulating air and wick away moisture.”
She also wears fewer layers when temperatures are higher and the wind is calm, but carries extra layers to put on during sudden changes. This usually includes a wind-blocking fabric or waterproof outer layer.
To prevent sweating, she checks her pace and avoids carrying excess equipment. “If we’re moving heavy gear or traveling between sites, we move very, very slowly and calmly,” she explains. “The worst thing that can happen at –55°F is starting to sweat."
Hydration and nutrition are also critical as the body burns more calories to maintain body temperature in colder climates. To offset this, Horvath eats a well-balanced meal before leaving shelter and then keeps warm and keeps her caloric intake up with warm drinks and by eating plenty of honey, chocolate, and energy bars throughout an expedition. Sleep is an often-overlooked factor. “Getting enough sleep is so important,” she says, “because without it, the body can’t regulate temperature or produce energy efficiently.”
Her team is also trained to never ignore the urge to urinate. “Your body uses a lot of energy holding it in,” she explains. “So, if you need to go, it’s important to go right away.”
In everyday life—whether skiing, hiking, or simply getting from place to place during winter—hypothermia risk can be reduced by limiting time outside, checking weather conditions beforehand, dressing appropriately, and planning nutrition and hydration needs in advance.
“No matter where you are,” Horvath says, “you need to be prepared and mindful of the early warning signs of hypothermia so you can get somewhere dry and warm as quickly as possible.”
Because for Esther Horvath, survival is not just preparation—it's awareness in action. In the coldest places on Earth, vigilance, knowledge, planning ahead, and maintaining respect for the body’s limits are often all that stand between life and disaster.
