Hypothermia is a core body temperature drop, and it happens faster than most people expect — wet skin in 50°F (10°C) air can be as dangerous as dry skin well below freezing, because water conducts heat away from your body roughly 25x faster than air.
Priorities, in order:
- Get dry. Wet clothing next to skin is the single biggest heat drain. Remove and wring out wet layers even if it's cold to do so briefly.
- Insulate from the ground. Anything — a pack, dry leaves, bark — under you matters more than anything over you, since conductive heat loss to cold ground is constant and direct.
- Layer for trapped air, not bulk. Loose, layered insulation traps warm air; tightly compressed insulation (like a sleeping bag stuffed too small) loses its value.
- Cover the head and neck. Significant heat is lost through areas with high blood flow close to the surface.
- Watch for the "umbles" — stumbling, mumbling, fumbling — early neurological signs of hypothermia. Someone showing these needs active rewarming (dry clothes, insulation, shared body heat, warm — not hot — fluids if conscious and able to swallow) and evacuation, not "walk it off."