Heat on the climb is not about the air; it is about the engine. During a steep ascent, skeletal muscles ramp up oxygen consumption and metabolic rate, dumping hundreds of watts of heat into the body’s core while cardiac output and skin blood flow surge to move that heat outward.
Overheating here is almost engineered by design. Sweating and vasodilation increase skin temperature, and sweat evaporation pulls latent heat from the skin surface, so the hiker can feel hot and drenched even when the ambient air would feel mild to a resting person in the same clothing and at the same altitude.
The ridge flips the physics. Stop moving, and metabolic heat production plummets while the soaked clothing and moist skin become a cold sink, especially once wind drives forced convection, stripping away the thin boundary layer of warm air hugging the body and accelerating both conductive and evaporative heat loss.
What felt safe on the climb becomes a liability. Wet fabric loses much of its insulating value, core temperature can start to fall, and wind chill can push the effective thermal load well below the thermometer reading, turning a stable environment into one that quietly promotes hypothermia.
