Heatstroke is your body overheating, usually as a result of prolonged exposure to or physical exertion in high temperatures. Heatstroke can require emergency treatment, as untreated it can quickly damage your brain, heart, kidneys and muscles. Symptoms High body temperature. Of 104 F (40 C) or higher, Altered mental state or behavior. Confusion, agitation, slurred speech, irritability, delirium, seizures and coma can all result from heatstroke. Alteration in sweating. In heat