Thus an oral temperature, measured with a thermometer placed under the tongue, is the most convenient and comfortable type of temperature measurement for adults. A normal oral temperature is 98.6°F or 37.0 °C.This is the accepted standard temperature for the normal body temperature. External measure of the body’s temperature such as axillary, tympanic membrane or skin temperatures are the least accurate and may take hours to reflect true changes in the body’s core temperature.hus an oral temperature, measured with a thermometer placed under the tongue, is the most convenient and comfortable type of temperature measurement for adults. A normal oral temperature is 98.6°F or 37.0 °C.