Definition
The temperature to which a parcel of air must be cooled, at constant pressure and water vapor content, for the air to become saturated. At that temperature, water vapor begins to condense into visible moisture such as dew, fog, or cloud.
Plain English
The temperature at which the air can't hold any more moisture. Cool the air down to this point and water starts forming — as dew on the ground, fog in the air, or cloud at altitude.
Context Anchor
Seen in aviation weather reports, forecasts, and preflight weather discussions, usually alongside the air temperature.
Derivation
From 'dew' (the moisture that forms on cool surfaces overnight) and 'point' (the specific temperature where it starts forming). The name describes exactly what it marks — the temperature at which dew appears.
Why Pilots Care
Indicates the likelihood of fog, low ceilings, frost, or carburetor icing that can reduce visibility and affect safety.
Grounding Statement
Imagine a cold drink on a warm day — the glass 'sweats' because the air touching it cools to its dew point and water condenses out. The same thing happens to the atmosphere when it cools to this temperature.
Intuition Check
Dew point is not the same as the current air temperature. It is the temperature the air would need to cool to before moisture starts forming visibly.
Example Sentence 1
The METAR showed a temperature of 12°C and a dew point of 11°C, so the pilot expected fog to form overnight.
Example Sentence 2
Because the dew point was only two degrees below the air temperature, the pilot prepared for reduced visibility on final approach.