What is the dew point?

• A. The temperature at which air becomes saturated
• B. The air's current humidity percentage
• C. The atmospheric pressure at sea level
• D. The rate of evaporation

Answer: (A)

Dew point is the temperature to which air must be cooled for water vapor to start condensing into liquid. At that point the air is saturated, holding as much moisture as it can. If cooling continues, condensation forms on surfaces as dew, fog, or clouds, depending on conditions. The dew point reflects how much moisture is already in the air—the higher the moisture, the higher the dew point, often close to the current air temperature. This is different from a humidity percentage, which tells how close the air is to saturation at the current temperature (relative humidity). It’s also not about atmospheric pressure or the rate of evaporation.