98.6 degrees Fahrenheit, or 37 degrees Celsius is approximately normal temperature for the human body.   The human body operates best at 98.6 degrees Fahreinheit (about 37o C). The healthy body temperature for humans is between 95 and between 99.3.he average human body temperature is 98.6º F or 37º C, but it can vary somewhat. Average adult temperature is 98.2º F (36.8º C). Older people average a bit less. These values can also vary with time of day.