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To prevent hypothermia on the trail, stay dry, block the wind, wear wicking layers you can adjust, and carry a waterproof shell, a warm jacket, a hat and gloves on every hike. Eat and drink regularly, turn back before bad weather sets in, and act on early signs like hard shivering and clumsy hands before they get worse.
Hypothermia is a drop in core body temperature that happens when you lose heat faster than you can produce it. It is not only a winter problem. The CDC notes that it can occur at cool temperatures above 40°F if someone is chilled by rain, sweat or cold water, and the National Park Service warns that sudden mountain storms can bring it on even in summer. This guide explains how it happens, how to prevent it, the warning signs to watch for and what to do if someone in your group gets too cold.
Key takeaways
- Hypothermia can happen in cool, wet and windy weather, not only in freezing temperatures.
- Wet and wind together are the biggest risk. Stay dry and block the wind early.
- Avoid cotton. Choose wicking base layers, an insulating layer and a waterproof shell.
- Eat, drink and keep moving at a steady pace to keep your body producing heat.
- Watch for early signs: shivering, fumbling hands, stumbling, slurred speech and confusion.
- Hypothermia is a medical emergency. Get help immediately if someone shows signs of it.
What causes hypothermia on the trail?
Hypothermia on the trail happens when your body loses heat faster than it makes it, and your core temperature drops. The most common causes are getting wet from rain, sweat or water crossings, strong wind that strips heat away, not wearing or carrying enough insulation, and running low on food, water or energy.
Your body loses heat in several ways, and outdoor conditions can speed all of them up:
- Conduction: direct contact with cold ground, rock or water.
- Convection: wind moving across your body and carrying heat away.
- Evaporation: sweat and wet clothing drying on your skin.
- Radiation: heat leaving your body into cold air, especially from an uncovered head.
- Respiration: breathing in cold air and breathing out warm air.
Water carries heat away from the body much faster than air, which is why being wet is so dangerous. A mild, rainy, windy day can be riskier than a dry, colder one if you are not prepared.
Who is most at risk of hypothermia while hiking?
Anyone can develop hypothermia, but risk is higher for hikers who are wet, tired, hungry, dehydrated or poorly dressed, and for children, older adults and people with certain health conditions. Alcohol raises the risk. Hikers caught by a storm, an injury or a delay far from the trailhead are especially vulnerable.
Situations that raise risk include:
- Hiking in cool, wet and windy weather without a waterproof shell.
- Sweating heavily on a climb, then stopping on an exposed ridge.
- Falling into or wading through cold water.
- Getting lost or injured and waiting a long time for help.
- Running low on food and energy late in the day.
- Underestimating conditions at higher elevations.
How do you dress to prevent hypothermia?
Dress to prevent hypothermia with a layering system: a moisture-wicking base layer, an insulating mid layer such as fleece or a puffy jacket, and a waterproof, windproof outer shell. Add a warm hat, gloves and dry spare socks. Avoid cotton, which holds water against your skin and loses its insulation when wet.
The goal is to stay dry from both outside moisture and your own sweat. Remove a layer before you start sweating heavily on a climb, and add one before you start to feel cold at a stop.
| Layer | Purpose | Good materials | Avoid |
|---|---|---|---|
| Base layer | Moves sweat away from skin | Merino wool, synthetic | Cotton |
| Mid layer | Traps warmth | Fleece, synthetic or down insulation | Heavy cotton sweatshirts |
| Shell | Blocks wind and rain | Waterproof, breathable fabric | Non-waterproof jackets in rain |
| Accessories | Protect head and hands | Wool or fleece hat, gloves | Leaving them in the car |
Down insulation is very warm for its weight but loses much of its warmth when wet, while synthetic insulation keeps more warmth when damp. Our guide to outdoor clothing layering basics explains each layer in more detail.
Tip: Add your shell and warm layer as soon as you stop for a break, then remove them when you start moving again. Staying slightly cool while hiking and warm while resting is the easiest way to avoid sweat and chill.
What gear should you carry to prevent hypothermia?
Carry a waterproof jacket, a warm insulating layer, a hat and gloves, spare dry socks, extra food and water, a headlamp, a map and an emergency blanket or lightweight bivy on every hike. In colder or remote areas, add rain pants, extra insulation and a way to make a hot drink.
The National Park Service advises packing a waterproof layer, a warm jacket, a warm hat, gloves and extra wool socks even in summer, because mountain weather can change quickly.
Hypothermia prevention packing list
- Waterproof, windproof jacket with a hood
- Rain pants for wet or cold forecasts
- Fleece or insulated jacket
- Warm hat and gloves
- Spare dry socks and base layer in a waterproof bag
- High-energy snacks and extra food
- Water, plus a warm drink in an insulated bottle on cold days
- Emergency blanket or bivy
- Sit pad or foam pad to insulate from cold ground
- Headlamp, map and charged phone
- Small first aid kit
How do food and water help prevent hypothermia?
Food and water help prevent hypothermia by giving your body the fuel it needs to produce heat. Eat small snacks regularly, especially foods with carbohydrates and fat, and drink steadily even when you do not feel thirsty. Hunger, dehydration and exhaustion make it harder to stay warm.
Cold weather can reduce thirst, and wearing gloves makes stopping to eat feel like a chore. Keep snacks in an easy-to-reach pocket and plan short, regular breaks.
- Eat a good meal before you start.
- Snack every hour or so on the trail.
- Drink regularly, even in cool weather.
- Carry a warm, non-alcoholic drink in an insulated bottle on cold days.
- Avoid alcohol, which can make you feel warm while increasing heat loss.
How do weather and planning affect hypothermia risk?
Weather and planning shape hypothermia risk more than anything else. Check the forecast for rain, wind and temperature at the elevation you will reach, start early, set a turnaround time and choose routes with sheltered exits. Turning back before you are soaked and chilled is the most effective prevention.
Temperatures usually drop as you climb, and wind is stronger on ridges and summits. A forecast for the trailhead can understate how cold it feels higher up. Our guide on how to prepare for changing trail weather explains how to read a forecast and spot warning signs.
- Check the National Weather Service forecast for the trail area.
- Note rain, wind and the lowest expected temperature.
- Pack for conditions colder and wetter than forecast.
- Tell someone your route and return time.
- Set a turnaround time and stick to it.
- Turn back early if you or anyone in your group is getting wet and cold.
Storms can bring lightning as well as cold rain. If you hear thunder, follow our lightning safety guide for hikers and campers.
What are the early warning signs of hypothermia?
Early warning signs of hypothermia include shivering, exhaustion, fumbling hands, stumbling, slurred speech, confusion, memory lapses and drowsiness. People with hypothermia often do not notice their own symptoms, so watch your hiking partners and speak up if someone seems clumsy, quiet, irritable or slow to respond.
The CDC lists shivering, exhaustion or feeling very tired, confusion, fumbling hands, memory loss, slurred speech and drowsiness as warning signs in adults. Many outdoor educators sum up the progression as the “umbles”: a person who stumbles, mumbles, fumbles and grumbles may be getting dangerously cold.
| What you may notice | What it can mean |
|---|---|
| Steady or hard shivering | The body is working to make heat |
| Fumbling with zippers or buckles | Hands and coordination are affected |
| Stumbling or slowing down | Body is cooling and tiring |
| Slurred speech or mumbling | Thinking and speech are affected |
| Confusion, poor decisions, irritability | Core temperature may be dropping further |
| Shivering stops while still cold | A serious sign that needs emergency help |
If shivering stops while a person is still cold and confused, their condition may be getting worse, not better.
What should you do if someone shows signs of hypothermia?
If someone shows signs of hypothermia, treat it as a medical emergency. Call for help, get them out of wind and rain, replace wet clothes with dry ones, insulate them from the ground, warm the center of the body first, and give warm, non-alcoholic drinks only if they are alert and able to swallow.
These steps are based on guidance from the CDC and the National Park Service:
- Call emergency services or send for help as soon as possible.
- Move the person to shelter, out of wind and rain.
- Remove wet clothing and replace it with dry layers.
- Place a pad, pack or other barrier between them and the ground.
- Warm the center of the body (chest, neck, head and groin) first, for example with skin-to-skin contact under loose dry layers or a sleeping bag.
- Give warm, sweet, non-alcoholic drinks only if they are fully alert. Never give drinks to an unconscious person.
- Keep them awake and handle them gently.
- Get professional medical care as soon as possible, even if they seem to recover.
If the person is unconscious or does not appear to be breathing, get emergency help immediately. The CDC advises starting CPR if needed and continuing until they respond or medical help arrives, while you keep warming them. Read the CDC hypothermia guidance for full details, and consider a first aid course from the American Red Cross before hiking in cold or remote areas.
How is hypothermia different from frostbite and heat illness?
Hypothermia is a drop in core body temperature that affects the whole body, while frostbite is freezing of skin and tissue, usually on fingers, toes, nose, ears, cheeks and chin. Heat illness is the opposite problem: the body overheats. Hikers can face cold and heat risks on the same day as weather changes.
Frostbite and hypothermia can happen together, so treat hypothermia first and protect cold areas from further exposure. Keep the nose, ears, fingers and toes covered with warm, dry clothing in cold, windy weather.
On hot days, the risk shifts to heat exhaustion and heat stroke. Our guide to heat safety for hikers covers the warning signs and how to prevent them.
What are common mistakes that lead to hypothermia?
Common mistakes that lead to hypothermia include wearing cotton, leaving the rain jacket or warm layer at home, sweating heavily and then stopping in the wind, ignoring the forecast, skipping food and water, and pushing on when someone in the group is wet and shivering. Most of these are easy to prevent with good habits.
- Trusting a sunny morning. Conditions can change quickly, especially at elevation.
- Wearing cotton. Jeans and cotton shirts stay wet and cold.
- Overheating on climbs. Sweat soaks your layers and chills you later.
- Waiting too long to layer up. Add warmth before you feel cold.
- Ignoring early signs. Clumsiness and confusion need action now.
- Not turning back. Pushing on while wet and cold makes recovery harder.
Frequently asked questions
Can you get hypothermia in summer?
Yes. Hypothermia can happen in summer, especially in the mountains, during cold rain, in strong wind or after falling into cold water. The CDC notes it can occur at temperatures above 40°F if you are wet and chilled. Always carry a waterproof shell, a warm layer, a hat and gloves, even on warm days.
What is the most important way to prevent hypothermia while hiking?
Staying dry is the most important step. Wear wicking layers instead of cotton, put on a waterproof, windproof shell before you get soaked, and avoid sweating heavily by adjusting layers as you go. Combine that with regular food and water and an early decision to turn back when the weather turns.
What are the umbles of hypothermia?
The umbles are a simple way to remember the early signs of hypothermia: stumbles, mumbles, fumbles and grumbles. A person may trip, slur their speech, struggle with zippers or buckles, and become irritable or withdrawn. If you notice these signs in someone, get them out of the weather and start warming them.
Should you give a hypothermic person alcohol to warm up?
No. Alcohol can make a person feel warmer while actually increasing heat loss, and it can affect judgment. Give warm, sweet, non-alcoholic drinks only if the person is fully alert and able to swallow. Never give drinks to someone who is unconscious, and get medical help as soon as possible.
Sources and further reading
- CDC: preventing hypothermia
- National Park Service: hypothermia, Rocky Mountain National Park
- National Weather Service for forecasts and cold weather alerts
- American Red Cross for first aid training
This guide gives general safety information, not medical advice. Your next step: build a layering system that keeps you dry and warm with our outdoor clothing layering basics.
