A measure of atmospheric moisture, also known as dew point temperature. It is the temperature to which air must be cooled in order to reach saturation, i.e. the point there air begins to condense and form dew, assuming that the air pressure and moisture content are constant. Usually given in Celsius or Fahrenheit degrees. Dew point is calculated using the dry bulb temperature and the wet bulb temperature given by a wet bulb thermometer or a psychrometer.