A rectal temperature is usually 0.9° F (0.5° C) higher than an oral temperature, and axillary and tympanic temperatures are usually 0.9° F (0.5° C) lower than an oral temperature. Agency policy usually specifies whether to document a temperature reading in degrees Fahrenheit or degrees Celsius.or repeated measurements or comparison of measurements over time, be sure to use the same site each time. There is no single temperature reading that is “normal” for all patients, although many consider an oral temperature of 98.6° F (37° C) the norm.