First comes “heat exhaustion,” mostly a mark of dehydration: profuse sweating, nausea, headache. After a certain point, though, water won’t help, your core temperature rising as your body sends blood outward to the skin, hoping desperately to cool it down. The skin often reddens; internal organs begin to fail. Eventually you could stop sweating. The brain, too, stops working properly, and sometimes, after a period of agitation and combativeness, the episode is punctuated with a lethal heart attack.
