Dew Point Temperature Frequently Asked Questions

By Bruce McDuffee

Dew point temperature (commonly referred to as ‘dew point’ or ‘dewpoint’) is the temperature at which water vapor in any gas at constant pressure begins to condense into liquid water at the same rate as it evaporates. If the air temperature is equal to or below the dewpoint, water condensation will occur meaning water vapor will transform from the vapor state into the liquid state. Condensed water will appear as dew on a surface and may also appear as a cloud or fog suspended in the air.

When the air temperature is equal to the dew point temperature, the air is at the saturation point and the relative humidity is 100%. The greater the difference between air temperature and dewpoint, the lower is the relative humidity.