What does ‘dew point’ mean?
The dew point is the temperature at which moisture in the air begins to condense.
Perhaps the air doesn’t seem damp at all. It does, however, have many tiny, invisible bits of water moving about in it. We call these tiny specks of moisture “water vapor.”
Cold air cannot hold as much moisture at warm air. When the air reaches the dew point, or below the temperature at which it can no longer hold all the moisture present, the moisture leaves the air and begins to condense on things.
The dampness of the cold air may cling to tiny specks of dust in the air and form fog or clouds. At night, the chilled leaves of plants may cool the air that touches them.
When the air is chilled below its dew point, it leaves one of its wetness on the plants as dewdrops.-Dick Rogers