High Quality Content by WIKIPEDIA articles! Heat illness or heat-related illness is a spectrum of disorders due to environmental heat exposure. It includes minor conditions such as heat cramps, heat syncope, and heat exhaustion as well as the more severe condition known as heat stroke.Heat stroke is 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.