Heat Stroke is a heat illness defined as a body temperature of greater than 40.6 C (105.1 F) due to environmental heat exposure with lack of thermoregulation. This is distinct from a fever, where there is a physiological increase in the temperature set point of the body. The term "stroke" in "heat stroke" is a misnomer in that it does not involve a blockage or a hemorrhage of blood flow to the brain. Treatment involves rapid physical cooling.