The dew point is the temperature at which a given volume of air must be cooled, at constant pressure, for it to become saturated with water vapor. In other words, it is the temperature to which the air needs to be cooled in order to achieve a relative humidity of 100%. At the dew point, the air cannot hold any more water vapor in the gas form, and if it is cooled further, water vapor will start to condense into liquid form, usually as fog or precipitation.
The dew point is a useful measure of the actual amount of water vapor in the air. Higher dew points indicate more moisture in the air, while lower dew points indicate drier air. This property makes the dew point an important factor in weather forecasting, as it can be used to predict the formation of dew, frost, fog, minimum overnight temperatures, and even rain, thunderstorms, and tornadoes.
The dew point can also affect human comfort. Higher dew points make the air feel more humid and can make it more difficult for the body to cool off in hot weather. On the other hand, lower dew points can make the air feel drier and more comfortable, especially in combination with lower temperatures.
