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HOW ARE DEW FORMED
Water vapour will condense into droplets depending on the temperature. The temperature at which droplets can form is called the dew point.

When surface temperature drops, eventually reaching the dew point, atmospheric water vapor condenses to form small droplets on the surface. This process distinguishes dew from those hydrometeors which are formed directly in air cooling to its dew point such as fog or clouds.

OR

Dew forms when a surface cools through loss of infrared radiation down to a temperature which is colder than the dewpoint of the air next to that surface.

Dew most often forms on on evenings or nights when there are few clouds, since the greenhouse effect from clouds can keep surfaces from cooling by infrared radiation loss to outer space. Calm winds at night also contribute to dew formation because a windy night keeps the lowest layers of the atmosphere warmer, and also helps evaporate any dew that might begin to form on surfaces.


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