Cold kills more people globally than heat in many temperate regions. Hypothermia can develop in temperatures well above freezing — even at 10°C (50°F) when combined with wind and wet conditions. A person can become critically hypothermic within 30 minutes in cold water. The danger of cold is that it gradually impairs the very thinking processes you need to survive, creating a downward spiral where victims make increasingly poor decisions.
Understanding how cold kills, how to prevent heat loss, and how to treat cold injuries is essential in any climate that experiences sub-zero temperatures or extreme winter weather.
How Cold Kills — The Physiology
The human body must maintain a core temperature of approximately 37°C (98.6°F). As core temperature drops:
| Core Temperature | Symptoms | Stage |
|---|
| 37–35°C (98–95°F) | Shivering, impaired coordination | Mild hypothermia |
| 35–32°C (95–90°F) | Intense shivering, confusion, slurred speech, stumbling | Moderate hypothermia |
| 32–28°C (90–82°F) | Shivering stops (dangerous sign), severe confusion, drowsiness | Severe hypothermia |
| Below 28°C (82°F) | Unconsciousness, cardiac arrest risk | Critical — life-threatening |
⚠️ When shivering stops, the situation is critical. Shivering is the body's last active defence against cold. Its cessation usually means the body can no longer generate heat effectively. This is a medical emergency.
Factors That Accelerate Heat Loss
| Factor | Effect |
|---|
| Wind chill | Strips away the warm air layer near skin — a 10°C day with strong wind can feel like -5°C |
| Wet clothing | Water conducts heat away from the body 25x faster than air |
| Exhaustion | Reduces ability to generate heat through shivering and movement |
| Alcohol | Causes blood vessels to dilate (feels warm) — actually dramatically increases heat loss |
| Wet head | Large proportion of heat lost through head — always wear a hat |
Clothing and Layering — The Foundation of Cold Survival
The layering system provides adjustable insulation and moisture management:
Base layer (next to skin):
- Purpose: Wick moisture away from skin
- Material: Wool or synthetic (polyester) — NOT cotton (cotton retains moisture and loses insulation when wet)
- Examples: Thermal long-underwear, wool socks
Mid layer (insulation):
- Purpose: Trap warm air
- Material: Fleece, down, or synthetic insulation
- Examples: Fleece jacket, down vest, insulated jacket
Outer layer (shell):
- Purpose: Block wind and rain while allowing moisture to escape
- Material: Waterproof and windproof but breathable
- Examples: Gore-Tex jacket, waterproof shell pants
⚠️ "Cotton kills" in cold weather. Cotton absorbs and holds moisture — wet cotton against your skin accelerates hypothermia rapidly. Avoid cotton as a base or mid layer in cold conditions.
Protecting Extremities
| Body Part | Minimum Protection |
|---|
| Head | Wool or synthetic hat covering ears |
| Hands | Waterproof, insulated gloves or mittens (mittens are warmer) |
| Feet | Wool socks + waterproof insulated boots; moisture-wicking sock liner underneath |
| Face | Balaclava or neck gaiter in extreme cold; protect nose and cheeks from frostbite |
Before a Winter Storm or Blizzard
Home Preparation
- Stock supplies for at least 72 hours — potentially a week in severe storms.
- Have alternative heating: wood stove, propane heater (safe for indoor use with ventilation), or extra blankets and sleeping bags rated for low temperatures.
- Check insulation on pipes — wrap exposed pipes with insulation to prevent freezing and bursting.
- Know how to shut off your water supply if pipes freeze.
- Charge all devices; have a battery radio for emergency broadcasts.
- Stock sand or gravel for traction on icy walkways.
- Clear snow from roof overhangs if safe to do so — heavy snow accumulation can cause roof collapse.
Vehicle Preparation
- Winter tyres or all-season tyres rated for ice and snow
- Emergency kit in your boot: blanket, water, energy bars, torch, shovel, jump leads, windscreen scraper, sand/kitty litter for traction
- Keep fuel tank above half-full in winter — fuel lines can freeze when tank is low
During a Blizzard
- Stay indoors. Blizzards can produce near-zero visibility (whiteout), making it impossible to navigate even a familiar neighbourhood. People regularly get lost and die within metres of their home.
- Avoid overexertion when shovelling — heavy snow is exhausting and sudden exertion in extreme cold is a leading cause of cardiac events.
- If you must go outside: tell someone where you are going and when you expect to return.
- Never run a generator, camp stove, gas stove, or charcoal grill indoors — carbon monoxide poisoning is a major cause of winter storm deaths.
- If your heating fails: close off all rooms except the one you are heating, hang blankets over doorways to reduce heat loss, and use body heat (multiple people under blankets together is very effective).
If You Are Stranded Outdoors or in a Vehicle
Outdoors
- Find or build shelter immediately — wind and precipitation are more dangerous than cold alone. A snow shelter (snow cave or quinzhee) can maintain interior temperatures around 0°C (32°F) even when outside is -30°C (-22°F).
- Insulate yourself from the ground — snow, leaves, or anything creates a barrier between your body and the heat-draining cold ground.
- Stay dry — if clothing is wet from rain or sweat, address this immediately. Wet clothing must be replaced or dried.
- Generate heat through movement — do exercises, but avoid sweating which will wet your clothing.
- Drink water — cold air is dry and dehydration occurs rapidly in winter.
In a Vehicle
- Stay with your vehicle — it provides shelter, visibility to rescuers, and resources.
- Run the engine 10 minutes per hour for heat — check that the exhaust pipe is clear of snow before each run (blocked exhaust causes carbon monoxide buildup inside the vehicle).
- Set the heater to recirculate cabin air when running.
- Turn on dome light when running engine — makes vehicle visible.
- Keep moving — clap, do foot exercises — to maintain circulation.
- Use a road flare or reflective triangle if you have one.
- Tie something bright to the vehicle antenna to help rescuers find you in snow.
Recognising and Treating Cold Injuries
Hypothermia First Aid
- Get the person out of the cold and wind.
- Replace wet clothing with dry clothing and blankets.
- Warm the core (torso) first — not the extremities (warming hands/feet first can divert cold blood to the heart and cause cardiac arrest).
- Use body heat — another warm person sharing a sleeping bag or blankets is highly effective.
- Give warm (not hot) sweet drinks if the person is conscious and alert — not alcohol.
- Do not rub the limbs — this can cause cold blood to move to the core.
- Seek medical care immediately for moderate to severe hypothermia.
Frostbite
Frostbite occurs when tissue freezes — most commonly fingers, toes, nose, ears, and cheeks.
Signs: Numbness, white or greyish-yellow skin, hard or waxy texture
Treatment:
- Get to a warm environment.
- Do NOT rub frostbitten tissue — this damages frozen cells.
- Do NOT thaw if there is a risk of refreezing — thawed tissue that refreezes suffers severe damage.
- If thawing is safe: immerse in warm (not hot) water at 37–39°C (99–102°F) for 20–30 minutes — this is painful.
- Seek medical care as soon as possible.
Quick Reference — Cold Survival
| Situation | Action |
|---|
| Cold, wet, windy outdoors | Remove wet clothing, add layers, seek shelter, eat for energy |
| Shivering person | Add insulation, share body heat, give warm sweet drinks if conscious |
| Shivering has stopped | Medical emergency — rewarm core, call emergency services |
| Stranded in vehicle | Stay with vehicle, run engine briefly with exhaust clear, stay visible |
| Blizzard — visibility near zero | Do not go outside — disorientation is rapid and can be fatal |
| Numb/white/waxy skin on fingers | Frostbite — warm gently in warm water, do not rub, seek medical care |
This guide is for general preparedness education. In a medical emergency, call local emergency services immediately. Cold injury management requires professional medical assessment — these guidelines are for emergency situations where professional care is not immediately available.