Relative Humidity (RH) describes the amount of water vapor held in the air at a specific temperature at any time, relative to the maximum amount of water vapor that air at that temperature could possibly hold. Air can hold more water vapor at higher temperatures than it can at lower temperatures.”

Dew point is the temperature at which water condenses with constant pressure and relative humidity. At a high RH, the dew point is closer to the current air temperature. A RH of 100% indicates the dew point is equal to the current temperature and the air is maximally saturated with water. When the dew point remains constant and temperature increases, RH will decrease. For example, at 18.3°C (65°F) dew point, the atmosphere feels sticky. The worst condition for a human is a high dew point of greater than 18.3°C (65°F) combined with high RH, whereas the best condition for a human is a 15.6°C (60°F) dew point and an RH of 50–70% at 23.9°C (75°F).