The human body typically maintains a healthy temperature in the range of 36.5–37.5 °C, but is affected by a range of factors including age, exertion, time of day, state of consciousness and emotional state.
When more heat is produced or absorbed than the body can dissipate, body temperature will climb and hyperthermia sets in at about 40 °C. Common symptoms of this life-threatening condition include headache, confusion, and fatigue.
In its mild form, hyperthermia is referred to as heat exhaustion, while severe hyperthermia is called heat stroke. Death is to be expected at 43 °C as severe brain damage and cardio-respiratory collapse occur, but at 44 °C death is almost certain.
At high levels of humidity, external temperatures above 34 °C cause human body temperature to rise, but in dry conditions it is possible to withstand up to 60 °C without adverse internal effects.