Hypothermia and frostbite: the two ways cold injures the body

Snow season is opening across the northern valleys, and winter trips to the mountains are back on everyone's plans. Cold is quiet compared to a storm — it does not roar or shake — and that is why it catches travellers out. Once heat loss outpaces heat production, the slide from uncomfortable to dangerous can take under an hour. This is part of our seasonal safety series — pair it with our dengue after the monsoon guide.

Hypothermia is a drop in the body's core temperature below 95°F (35°C), at which point organs such as the brain, heart and kidneys can begin to malfunction, according to the US Centers for Disease Control and Prevention. It does not need blizzard conditions: wind, wet clothing and exhaustion can drag the core down in temperatures many people would call merely cold. Frostbite is the freezing of skin and tissue, most often in fingers, toes, noses and ears — the parts furthest from the body's warm core. Britain's NHS notes it can set in when exposed skin meets temperatures of 0°C (32°F) or below. The two often travel together, so a traveller found with frostbite should always be checked for hypothermia too.

The moment shivering stops

Shivering is the body's alarm bell: muscles burning fuel to make heat. Early signs include shivering, exhaustion, confusion, fumbling hands, memory loss, slurred speech and drowsiness. The danger sign is when shivering stops — not recovery, but the body running out of fuel. Then come loss of coordination, confusion, slowed pulse and breathing, and eventually unconsciousness.

If hypothermia is suspected, treat it as an emergency and get medical help immediately. The US Forest Service advises getting the person into a warm room or shelter, removing any wet clothing, and warming the centre of the body first — chest, neck, head and groin. Warm drinks can help raise body temperature, but never give alcohol, and never try to give drinks to someone who is unconscious. Handle the person gently: with severe hypothermia the heart is fragile. Even if a victim appears lifeless with no detectable pulse, CDC guidance says CPR should be given and continued while warming, until the person responds or medical aid takes over.

Wet clothes are more dangerous than cold air

What actually kills in cold weather is rarely the thermometer reading — it is water. Wet clothing pulls heat from the body far faster than dry air, and sweat counts. The classic mistake: overdressing at the start of a trek, sweating through the base layer on the climb, then freezing on the descent in damp clothes.

The layering system exists to solve exactly this: the base layer sits next to the skin and moves moisture away — avoid cotton, which absorbs water and dries slowly; the mid layer insulates, with wool and fleece holding heat far better than cotton; the outer layer blocks wind and water. The Canadian Red Cross adds the forgotten details: cover exposed areas — fingers, cheeks, ears, nose — change out of wet clothes fast, and avoid tight clothing that restricts circulation. Mittens beat gloves because fingers warm each other. And the CDC's prevention advice is blunt: wear a wind barrier, stay dry, avoid alcohol — it feels warming but accelerates heat loss and dulls the judgement that would get you to shelter.

Rewarming frostbite: what helps, what harms

Early signs: skin that feels cold and firm, numbness, or a stinging or burning sensation, with skin red or pale. It is serious when skin turns hard and frozen, white, blue or blotchy, or when blisters filled with clear, milky or bloody fluid appear — these need emergency care, as does any combination with hypothermia symptoms.

Move to a warm place, remove clothing and jewellery such as gloves, rings and boots from the area, and rewarm in warm — not hot — water, roughly 40 to 42°C (104 to 108°F), for up to 30 minutes or until normal colour returns. Then dry and cover lightly with a clean dressing if you have one. What you must not do matters as much: do not rub frostbitten tissue, do not use direct heat such as a fire or hot plate, and do not break blisters. Do not rewarm at all if the area could refreeze before reaching care — thawing and refreezing causes far worse damage. Frostbite that looks deep always needs a hospital, not a home remedy — the same rule we stress in our snakebite first aid guide.

A winter trip checklist that actually works

Most cold-weather emergencies are not caused by freak weather but by a small oversight that snowballs:

  • Share your plan. Tell someone exactly where you are going and when you expect to be back. A missed return is what triggers a search.
  • Check the forecast and the wind chill, not just the temperature. The US National Weather Service notes that at 5°F with 50 mph winds the wind chill is -24°F and exposed skin can freeze within 30 minutes — at -5°F with 35 mph winds, it can happen in 10. Wind is the multiplier, and winter storms bring lightning and hail hazards of their own — see our thunderstorm and hail safety guide.
  • Pack an emergency warmth kit — the same go-bag logic as our earthquake go-bag guide: dry spare layers in a waterproof bag, a thermal blanket, a head torch, a charged phone bank and water. It lives in the vehicle or the daypack, not at the hotel.
  • Dress for the stop, not the walk. You generate heat moving; you lose it standing still. Carry the extra layer for the summit photo, the queue and the breakdown.
  • Keep the vehicle winter-ready if you are driving: half a tank of fuel, blankets, and never run the engine for heat in a snow-blocked exhaust situation — the same winter-road caution as fog driving applies to snow and ice.
  • Travel with company when you can. A companion is the only reliable early-warning system for confusion and clumsiness — the hypothermic brain cannot diagnose itself.

What our records show, and what they miss

Our live tracker records cold waves as their own incident type, and the archives show a repeating pattern: the deadliest cold events are rarely famous blizzards, but quiet overnight cold snaps that catch people in poorly heated rooms — the same season that drives the gas heater and geyser dangers we covered in our pre-winter guide — stranded vehicles and thin clothing. Where official tallies exist they confirm the scale — the US CDC recorded an average of about 699 hypothermia deaths per year from 1979 to 1998 — but that figure is decades old and no current global count exists. What the records miss is bigger: frostbite injuries almost never make official statistics, near-misses go unreported everywhere, and in many countries cold deaths are filed under other causes.

The short version

  • Hypothermia starts when core temperature drops below 95°F (35°C) — and shivering stopping is a danger sign, not a recovery. Get emergency help, get to shelter, remove wet clothing, warm the body's centre first.
  • Frostbite freezes skin and tissue — fingers, toes, nose, ears first. Rewarm gently in warm (40–42°C) water; never rub, never use direct heat, never break blisters, and do not rewarm if refreezing is possible.
  • Wet clothing kills faster than cold air: layer up (moisture-wicking base, insulating middle, windproof waterproof outer), avoid cotton, change out of anything damp fast.
  • Check the wind chill, not just the temperature — wind can turn merely cold air into a frostbite risk within minutes.
  • Share your route, carry dry spare layers and a thermal blanket, and travel with company: the cold-impaired brain cannot judge its own danger.