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Understand heat loss and wet clothing
Lesson 1 of Warmth, Shelter and Weather. Anyone can read this lesson with no account. Every lesson after this one is for students.
Dry warmth and cold-illness recognition
Identify heat-loss routes and control sweat before ordinary work becomes unsafe.
Understand heat loss and wet clothing
After this lesson you can name the four ways your body loses heat, match each to a fix, and plan a cold-weather chore so you stay dry.
1What you need
Paper, a few clothing items you own, and a chore you do in cold or wet weather (carrying wood, shoveling, feeding animals). Stay indoors and comfortable for this lesson.
2Four ways heat leaves your body
| Route | What happens | Example | Fix |
|---|---|---|---|
| Conduction | Heat flows into whatever you touch | Sitting on a cold step | Pad or insulation between you and the cold surface |
| Convection | Moving air or water carries heat away | Wind through a sweater | Wind-resistant outer layer; shelter |
| Evaporation | Drying sweat or rain uses body heat | Damp shirt after shoveling | Stay dry; vent before you sweat |
| Radiation | Heat leaves toward cooler surroundings | Standing in an open yard on a clear night | Insulating layers; hat |
All four happen at once. A coat helps with wind and radiation but does nothing for a cold step.
3Wet clothing
Rain is one source. Sweat is often the bigger one: you work hard, soak your base layer, then stop and chill. Wet clothing loses much of its insulation. Wool and synthetic fabrics handle moisture better than cotton for active cold work, but no fabric keeps you safe when soaked for a long time.
CDC notes hypothermia can happen even above 40°F when someone is chilled by rain, sweat or cold water. A mild forecast does not cancel the risk of wet clothes.
Alcohol does not warm you. It can make you feel warm while you lose heat.
4Before, during, after
- Before: check the weather. Put dry spare clothes inside where you will finish. Tell someone what you are doing.
- During: open zippers or take off a layer before you start sweating heavily. Slow down. NWS warns against overexertion in winter, especially shoveling snow if you have heart or breathing problems.
- After: go inside, change out of damp clothes right away, then rest and eat.
5Worked example
Alex carries six boxes from the porch on a cool, drizzly day, wearing a heavy coat over a sweatshirt. After the first trip Alex is sweating. Alex steps inside, swaps the sweatshirt for a thin synthetic top under the coat, unzips the coat partway and finishes at an easier pace. Dry clothes are waiting by the door. If Alex gets shaky, clumsy or confused, the chore stops.
6Practice
- Draw a person doing your chore. Label where each of the four heat losses happens.
- Next to each, write which item you own addresses it.
- Write your before-during-after plan for that chore.
- Optional real practice: the next time you do the chore, put dry clothes by the door first, vent before sweating, and change as soon as you come in. Note how you felt.
Expected result: a labeled drawing and a three-step plan. Do not get wet or cold on purpose to test it.
7Self-check
1. Which route does a sleeping pad mainly stop?
Show answer
Conduction into the ground.
2. Why vent before you sweat heavily?
Show answer
Wet clothing makes you lose heat fast once you stop working.
3. Can hypothermia happen at 45°F?
Show answer
Yes, especially when wet.
8Keep for your binder
Save the drawing and plan. Next lesson builds the clothing layers themselves.
Continue with the full course
This free preview is lesson 1 only. Enroll to open the rest of Warmth, Shelter and Weather.