Hypothermia: Signs, Prevention & Treatment Every Hiker Should Know

Hypothermia is one of the most dangerous — and most misunderstood — backcountry hazards. The misconception that kills people: you think you need snow and freezing temps. You don’t. Most cases happen in wet, windy 30–50°F weather to people who aren’t dressed for it. Here’s how to recognize it, prevent it, and treat it in the field.

What Hypothermia Actually Is

Hypothermia is when your core body temperature drops below 95°F (35°C) — your body is losing heat faster than it can produce it. Left unchecked, your systems slow down and it becomes life-threatening. The drivers are almost always a combination of:

• Cold (and it doesn’t have to be that cold)
• Wet (rain, sweat, a creek fall — wet skin loses heat ~25× faster)
• Wind (strips away your warm layer of air)
• Exhaustion & underfueling (no fuel = no heat)

The classic killer is “cotton + rain + wind” on a cool day. Cotton holds water against your skin and stops insulating — hence the saying “cotton kills.”

Know the Signs: “The Umbles”

The easiest way to remember early hypothermia: the umbles.

• St-umbles — clumsiness, poor coordination
• M-umbles — slurred speech
• F-umbles — can’t work zippers, buckles, fingers
• Gr-umbles — irritability, confusion, bad decisions

The stages

Mild: uncontrollable shivering, cold/numb hands, the umbles, fatigue. (Easiest to reverse — act now.)

Moderate: violent shivering that may then stop (a bad sign, not a good one), worsening confusion, slurred speech, drowsiness, stumbling, poor judgment.

Severe: shivering stops entirely, muscles stiffen, slow/weak/irregular pulse, loss of consciousness. Sometimes “paradoxical undressing” (feeling hot and removing clothes). This is a life-threatening emergency.

⚠️ When shivering stops but the person is still cold and confused, that’s worse, not better — the body has lost the ability to warm itself.

Prevention (Where the Real Safety Is)

• Stay dry. A quality rain shell, and know how to keep your gear dry. Keep a dry insulating layer you never hike in.
• Ditch cotton. Wear wicking synthetic or merino base layers — see the layering system.
• Layer smart & manage sweat — shed layers before you sweat through them; sweat-soaked clothes chill you fast when you stop.
• Eat and drink constantly — your body needs fuel and water to make heat.
• Avoid total exhaustion — turn around with energy in reserve.
• Check the forecast and pack for worse — carry an emergency bivy/space blanket and extra insulation, even in summer.

How to Treat It in the Field

For mild hypothermia (still shivering, alert):

1. Stop the heat loss — get out of wind and rain, into a tent or shelter.
2. Remove wet clothes, replace with dry layers.
3. Add insulation — sleeping bag, extra layers, and insulate from the ground (a pad — the ground steals huge heat).
4. Add heat — warm, sweet, non-alcoholic drinks (if fully alert), chemical hand/body warmers or hot water bottles placed at the core (armpits, chest, neck, groin — not the limbs), and skin-to-skin contact in a bag.
5. Feed them carbs/sugar for fuel.

For moderate to severe (shivering stopped, confused, drowsy, or unconscious):

• Handle very gently — rough movement can trigger cardiac arrest in a severely cold person.
• Do NOT give food or drink to someone who isn’t fully alert (choking/aspiration risk).
• Do NOT rub the limbs or put them in hot water — that can rush cold blood to the core (“afterdrop”).
• Insulate them completely (a “hypothermia wrap”: pad underneath, dry layers, sleeping bag, then a waterproof outer layer) and evacuate / call for rescue immediately — use a satellite communicator where there’s no cell signal.

Never give alcohol — it dilates blood vessels and accelerates heat loss.

The Bottom Line

• It doesn’t take snow — wet + wind + cool temps is the real danger, even in summer.
• Watch for shivering + the umbles; treat it the moment it appears.
• Stay dry, skip cotton, eat, and carry backup insulation — prevention beats treatment every time.
• Shivering stopping is an emergency — insulate, handle gently, and get help.

Related Guides

• The Complete Backcountry Layering System
• How to Keep Your Gear Dry in the Rain
• How to Stay Warm Sleeping in a Tent
• Best Satellite Communicators

Stay dry. Stay warm. Stay alive.