Hypothermia: How to Spot It Before It Decides for You
Shivering stops long before the danger does. Here is how to stage hypothermia, treat it with what you have, and keep it from starting.
Hypothermia is a drop in core temperature below 95 °F (35 °C). Mild cases shiver hard and fumble; moderate cases stop shivering but get confused and clumsy; severe cases lose consciousness. Treat mild cases with dry layers, shelter and warm sweet drinks. Handle moderate and severe cases gently, rewarm the core first, and evacuate — do not walk a severely hypothermic person out.
More people die of cold in the backcountry than of falls, avalanches or lightning. It rarely arrives as a dramatic storm. It arrives as a wet afternoon, a long descent, a wind that picks up while you are eating lunch — and a decision you make too late because the person in trouble is the last to notice.
The staging that matters
Core temperature is the only number that matters. Everything else — how the person feels, how hard they are shivering — is a symptom of it.
| Stage | Core temp | What you see | What to do |
|---|---|---|---|
| Mild | 95–90 °F (35–32 °C) | Violent shivering, numb hands, fumbling with zippers, poor judgment | Dry layers, shelter from wind, warm sweet drink, keep moving |
| Moderate | 90–82 °F (32–28 °C) | Shivering stops, confusion, stumbling, slurred speech | Build shelter immediately, apply heat to armpits and groin, no walking out |
| Severe | Below 82 °F (28 °C) | Unconscious, slow shallow breathing, may undress | Handle as gently as a spinal injury, evacuate, no field rewarming |
Shivering stopping is not improvement. It means the body has given up generating heat. This is the single most common misread in the field, and it is the one that kills.
The "umbles" — an early warning checklist
Experienced leaders watch for four words, because each one is a stage transition you can still reverse:
- Grumbles — the person gets irritable and withdrawn
- Fumbles — fine motor control goes; they cannot work a zipper or a stove
- Stumbles — gross motor control goes; they trip on flat ground
- Mumbles — speech slurs; cognition is degrading
Any of the four means stop, feed, dry and warm. Do not "push on to camp."
Treating mild hypothermia
Get the person out of the wind, out of wet layers, and into dry insulation. Feed them warm, sweet liquid — the sugar matters as much as the heat, because it restores the fuel the body is burning to shiver. Keep them moving if they can move safely, but do not let them work up a sweat: sweat is the mechanism that got you here.
Treating moderate and severe hypothermia
- Build shelter before you do anything else. Wind and wet will outrun any amount of added clothing.
- Heat the core, not the extremities. Chemical warmers, hot water bottles wrapped in cloth, or a warm body against the chest, armpits and groin. Warming hands and feet first pulls blood away from the core.
- Handle gently. A cold heart is irritable. Rough handling, jostling during a carry, or forcing a severely hypothermic person to walk can trigger cardiac arrest.
- Do not walk out a severe case. Package them, insulate from the ground, cover the head, and call for evacuation.
- Do not give food or drink to an unconscious person, and do not rub the limbs.
Prevention, which is where the real work is
- No cotton next to skin. Cotton holds water against the body and stops insulating. Wool or synthetic base layers only.
- Vent before you sweat. Open the shell on the climb, close it on the descent. The goal is to stay dry, not to stay warm while moving.
- Carry insulation you never wear while moving. A dry down or synthetic puffy in a waterproof bag is a rescue tool, not a spare layer.
- Wind is a multiplier, not an addition. Blocking wind is worth more than adding thickness. A windproof shell over a modest midlayer beats a thicker midlayer in the open.
- Eat and drink on a schedule. Dehydration and calorie deficit both impair shivering and judgment.
This is general guidance, not a substitute for a Wilderness First Responder course or professional medical care. If someone is confused, not shivering, or unconscious, treat it as an emergency and get help.