What is dew point temperature?
The dew point temperature is the temperature air has to be cooled to reach saturation. This is why humidity levels rise dramatically at night when temperatures drop, which explains why dew forms in the early morning hours. At night, terrestrial thermal radiation is lost (radiational cooling) which chills the air above the ground thus bringing it closer to dew point. Moisture levels change constantly, so there are actually two ways to reach saturation (100% RH). One way is if air temperature drops (assuming humidity stays constant). The other way is if ambient temperature is constant, then added moisture to an air mass can cause that mass to reach its saturation point.
