Humans are warm-blooded (homeothermic endotherms) i.e. we maintain a uniform body temperature by internal generation of heat. A stable body temperature results from a balance between internal heat production and heat loss to the environment. The brain processes input from peripheral and central thermal sensors regulating body temperature by keeping a balance between heat production and heat loss.
At rest, humans produce 40-60 kilocalories (kcal) of heat per square meter of body surface area due to cellular metabolism. Heat production increases with movement (shivering increases the rate of heat production 2-5 times). Heat is lost or gained through several physical mechanisms, including radiation, conduction, convections, and evaporation. Radiation may account for 55%-65% of loss, evaporation 30%, and conduction 15%, with convection being a relatively minor component.
Normal body temperature depends on when, where, and in whom it is measured. The normal range for body temperature is 97 to 100 degrees Fahrenheit or 36.1 to 37.8 degrees Celsius (actually 98.2 plus or minus 0.6 i.e. 97.6° to 98.8° F).
The normal range of human body temperature varies due to an individuals metabolism rate, the higher it is the higher the normal body temperature or the slower the metabolic rate the lower the normal body temperature. Other factors that might affect the body temperature of an individual may be the time of day or the part of the body in which the temperature is measured at. The body temperature is lower in the morning, due to the rest the body received and higher at night after a day of muscular activity and after food intake. Body temperature also varies at different parts of the body. Oral temperatures, which are the most convenient type of temperature measurement, is at 37.0 °C. This is the accepted standard temperature for the normal core body temperature. Axillary (armpit) temperature is an external measurement taken in the armpit or between two folds of skin on the body and is about 97.6 °F or 36.4 °C. Rectal temperature is an internal measurement taken in the rectum, which falls at 99.6 °F or 37.6 °C.
Persistently low body temperature may be due to hormonal factors or other disease. If you are asymptomatic, just ignore it as this is the normal level for you.