A Vermont Dial Thermometer offers a display of both temperature and humidity, in an easy to read format.  The hygrometer measures the moisture content of the air to determine the relative humidity.  These mechanical hygrometers take advantage of a time-tested method in which a synthetic fiber expandes as it absorbs moisture from the air.  This expansion, in turn, moves the metal coil to which it is bonded.  As the coil twists, the pointer moves up the scale.  As the fiber dries, the coil contracts and the pointer reverses direction. Relative humidity ranging from 45% to 70% is generally considered to be comfortable.  Exterior is copper, will not peel flake or rust.  Manufacturer guarantees this weather station for life.