Dew Point

Dew Point is a saturation temperature. It's the temperature that humid air needs to be cooled for water vapor to be condensed into water, the water is then called dew. Dew point is associated with relative humidity; It helps indicate when the dew point is close to the current air temperature.


History of Dew Point

Dew point was believed to be discovered by John Dalton (1766- 1844). Along with other theories, dew point was presented in one of four important papers in 1801. He was born and raised in England, so it is believed that is where he developed the idea of dew point.

Application of Dew Point

Dew Point is used to find the temperature at which water condenses. The temperature is mostly obtained by using tables; to do so you need to know the the temperature of the air (dry-bulb temperature) and the temperature to which evaporation forms on the thermometer bulb (wet- bulb temperature). When the two are connected to a frame, it's called either a psychrometer or a sling psychrometer. Most weather bureau stations have a tele- psychrometers that automatically record both. The dry- bulb and the wet-bulb temperature help find the dew point (the greater the difference between the two, the faster the evaporation). The point water condenses is the dew point. An easier way to find the dew point is using dewell, it automatically registers the dew point.


  1. Beiser, A. (1988). Physical Science (2nd Edition). New York, NY: McGraw Hill
  2. Dew Point facts, Discussion Forums, and Encyclopedia Article.
  3. DeLong and Koeppe (1958). Weather and Climate. NY, Toronto, London: McGraw Hill
  4. what- when-

This WikiPage developed by Amber McGinnis 2011FA