Key takeaways
- Hypothermia is a core temperature below ~95°F (35°C) — a whole-body cold emergency.
- It's driven by cold, wet, and wind, not just freezing temperatures; you can get it well above 32°F.
- Early signs are shivering and the 'umbles' (stumbling, mumbling, fumbling, grumbling); severe cases stop shivering.
- Treat by stopping heat loss, removing wet clothing, insulating, and warming — severe cases need urgent evacuation.
This is general educational information, not medical advice. In an emergency, seek professional medical help and call for rescue.
What causes hypothermia
Hypothermia sets in when your body loses heat faster than it can generate it, dropping your core temperature. The biggest culprits are being cold, wet, and windy — wet clothing and wind strip heat many times faster than dry, still air, which is why hypothermia commonly happens in cool rather than freezing conditions. Exhaustion, dehydration, and lack of food make it worse.
Signs and stages
- Mild: vigorous shivering, cold pale skin, and the ‘umbles’ — stumbling, mumbling, fumbling, grumbling.
- Moderate: intense shivering gives way to slowed movement, slurred speech, and poor judgement.
- Severe: shivering stops, consciousness fades — a life-threatening emergency.
A hiker caught in cold rain starts fumbling zippers and answering oddly. Their partner gets them under shelter, swaps the wet base layer for dry insulation, adds a hat and shell, and gives warm sweet fluids — reversing mild hypothermia before it worsens.
Field response & prevention
Stop the heat loss first: shelter from wind, remove wet layers, insulate, and add core warmth. Prevent it by managing your layering to stay dry, eating and drinking, and carrying extra insulation from the Ten Essentials. The related cold injury is frostbite; see hypothermia vs frostbite.
The bottom line
Hypothermia is a whole-body cold emergency that most often strikes in cool, wet, windy conditions rather than deep freezes. Catching the early 'umbles' and acting fast — dry insulation, shelter, warmth, calories — usually reverses it; severe cases are life-threatening and need urgent professional care. Prevention through layering and staying dry is far easier than treatment.
Frequently asked questions
What are the signs of hypothermia?
Early hypothermia shows as vigorous shivering, cold pale skin, and the 'umbles' — stumbling, mumbling, fumbling, and grumbling — reflecting impaired coordination and judgement. As it worsens, shivering may stop, confusion deepens, and the person becomes drowsy and unresponsive, which is a medical emergency.
How do you treat hypothermia in the field?
Stop further heat loss: get out of wind and cold, remove wet clothing and replace with dry insulation, add a hat and a wind/waterproof layer, and add external heat to the core. Give warm sweet drinks if fully alert. Severe hypothermia (no shivering, altered consciousness) needs gentle handling and urgent evacuation.
Can you get hypothermia above freezing?
Yes. Most hypothermia happens in cool, wet, windy conditions well above freezing, because water and wind strip heat far faster than still, dry cold. 'Cold, wet, and windy' is the dangerous combination to respect even at 40–50°F.
Sources
- Hypothermia & cold — CDC
- Cold injuries — Wilderness Medical Society
- Cold-weather safety — National Park Service