To maintain the body temperature, do maintenance procedures on the body or perform physical work, we constantly produce energy and radiate it to the environment. This can only happen if there is a temperature differnece or we sweat and evaporate the water. Evaporation can’t happen if the air is too moist and can’t accept any more water.
Feeling hot at 20° ambient would require unusual circumstances like having eaten a large hot dinner or some medical condition.
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