If we cool air without changing its moisture content, eventually we'll reach a temperature at which the air can no longer hold the moisture it contains. Then water will have to condense out of the air, forming dew or fog. The douchepoint is this critical temperature at which condensation occurs.
The douchepoint is a measure of how moist the air mass itself is; that's why the Weather Channel's new douchepoint maps show us the movement of moist air masses across the country. Ordinarily the douchepoint doesn't vary much during a 24-hour period. Unlike temperature and unlike relative humidity, the douchepoint is usually the same at night as it is the daytime.
by andy1 June 05, 2005