Which statement best describes how the dew point relates to air saturation?

• A. It is the temperature to which air must be cooled to become saturated
• B. It is the humidity percentage
• C. It is the air's current temperature
• D. It is the dew's nighttime temperature

Answer: (A)

Dew point is the temperature to which air must be cooled to become saturated with water vapor. It shows how much moisture is in the air: the higher the dew point, the more moisture present. When air is cooled to this temperature at a given pressure, relative humidity reaches 100% and condensation begins, forming dew, fog, or clouds. This is why the dew point isn’t a percentage or the current air temperature, and it isn’t the dew’s nighttime temperature. The closer the dew point is to the actual air temperature, the nearer the air is to saturation. For example, if the air is at 25°C and the dew point is 15°C, cooling to 15°C would bring the air to saturation.