The body's temperature often changes due to metabolism. The rate of metabolism changes slightly during different times of the day, so the body's temperature may change because of the time of day. For example, temperature will most likely be lower in the morning, due to the rest period of sleep, and higher at night, because of muscular activity and food intake during the day. Also, body temperature will vary depending on where you take the temperature. For example, putting a thermometer in your armpit will make your temp a little lower, but taking a rectal temp will be a little higher.