As used by the Weather Bureau in determining degree days, the average of the maximum and the minimum dry-bulb atmospheric temperatures in degrees Fahrenheit recorded for each day.
The arithmetic mean between hot and cold surface temperatures of an insulated pipe, duct or vessel. tm = (t1 + t2)/2.
The normal temperature over a given period of time as calculated from the mean of all days sampled. It is often given as a mean high or low temperature for a given month.