The temperature 98.6 degrees Fahrenheit is equal to 37 degrees Celsius. This represents the commonly accepted average normal body temperature for humans, although studies suggest that a wider diversity of average body temperatures exists for some people.
Body temperatures change in response to a variety of situations. Being in excessively high temperatures overloads the body's ability to maintain a constant temperature by cooling down, thus raising body temperature. This is a dangerous and life-threatening condition as it can cause heat stroke and brain damage. Likewise, excessively low temperatures first cause shivering, an involuntary muscle contraction designed to generate warmth, before the body begins to cool. Hypothermia, also a life-threatening condition, then sets in.