Body temperatures vary from person to person and fluctuate during the course of the day. Therefore, it helps to know one's normal, healthy temperature to determine the temperature range of a fever.
Different measurement sites (rectal, axillary, oral, frontal, and auricular) will give different readings. As such, measurements taken from different sites might not be comparable. Generally,
- An ear (tympanic) temperature is 0.5 °F (0.3 °C) to 1 °F (0.6 °C) higher than an oral temperature.
- An armpit (axillary) temperature is 0.5 °F (0.3 °C) to 1 °F (0.6 °C) lower than an oral temperature.
- A forehead (temporal) temperature is 0.5 °F (0.3 °C) to 1 °F (0.6 °C) lower than an oral temperature.
- Source: University of Michigan Health C.S. Mott Children’s Hospital https://www.mottchildren.org/health-library/tw9223
Other issues that can affect the forehead temperature are sweat, air temperature, hair, if a person's head has been covered.