The Dew Point

Q: What does the dew point tell us about current weather conditions?

A: "The dew point is the temperature to which the air would have to cool in order to reach saturation," explains Brent McRoberts of Texas A&M University. "The dew point tells us the amount of water vapor in the air. The higher the dew point, the higher the water vapor content. In other words, dry air has a low dew point, whereas moist air has a higher dew point."

Q: Does the dew point help in predicting the weather?

A: "Yes, condensation occurs when the temperature of the air is lowered to its dew point," adds McRoberts. "Because of this, we can tell when the air temperature is dropping and when the air is approaching saturation. If we predict the air temperature to reach its dew point, that means we think the air is going to be saturated. In turn, if we expect the air to be saturated, then we would expect water vapor to condense to liquid water droplets, clouds to form and possibly precipitation. So in short, the dew point is a key element in predicting clouds and precipitation."

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