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Temperature, Humidity and the Dew Point

Meteorologists and other weather forecasters discuss the amount of moisture in the air using two different measures: dew point and relative humidity. While relative humidity fluctuates with changes in temperature, dew point does not, making it the preferred measure for many scientists.

Dew Point
- The dew point is the temperature at which air will be saturated with moisture and will begin to convert some of its water vapor to water droplets, such as dew. The dew point is never higher than the temperature.
Relative Humidity
- Unlike dew point, relative humidity is expressed as a percentage. Air with a 60 percent relative humidity is holding 60 percent of the moisture it could hold. When the temperature falls to the dew point, the relative humidity is 100 percent.
Calculation
- Temperature, relative humidity and dew point are all related. If you have two of the three values, you can calculate the third. A website such as that provided by the Department of Atmospheric Science at Colorado State University will help. According to its equations, for instance, a day with a temperature of 64 degrees Fahrenheit and a dew point of 58 degrees F would have a relative humidity of 80 percent.

Nature