A Intermountain Healthcare answered. A normal temperature measured by mouth is 98.6 degrees Fahrenheit (37 degrees Celsius) and can be between 97 degrees Fahrenheit to 99 degrees Fahrenheit (36.1 degrees Celsius to 37.2 degrees Celsius).This is because different people have different normal body temperatures. child's temperature can vary depending on the time of day (it's nearly 2 degrees lower in the early morning than in the late afternoon or early evening), how much food she has eaten, how much sleep she's gotten, or whether she has a fast or slow metabolism.