Normal body temperature is in the range of 36.5–37.5 °C on the average, although it varies somewhat among individuals (gender, age). Additionally, temperature can vary according to physical activities, throughout the day, & due to external factors, e.g. with the change of seasons. Normal body temperature may change during any given day. It is usually highest in the evening. Body temperature is typically elevated after physical activity.
Body temperature is a basic condition for the proper operation of the cells. It is configured by many internal organs with the control of the nervous system on the delicate balance of heat production & heat loss. This mechanism (called thermoregulation) ensures the stable operation of vital functions by keeping the body at optimum operating internal temperature.