What is the main reason for less dew formation on a cloudy night?

Correct answer: Clouds reduce radiational heat loss from the surface

Correct answer: A. Dew forms when a surface loses heat, usually by radiation on a clear, calm night, and cools to its dew point. At that point, nearby water vapour condenses into liquid droplets on grass, leaves, roofs, or other surfaces. Clouds act like a cover: they absorb and re-radiate some outgoing terrestrial radiation back toward the surface. Thus the ground loses heat more slowly and often does not cool enough to reach the dew point, so less dew forms. A is correct. B is wrong because clouds do not destroy water vapour; they contain condensed water and may coexist with moist air. C is wrong because clouds do not always make surfaces colder than the freezing point; their insulating effect often limits cooling. D is wrong because clouds do not remove all condensation nuclei. Memory cue: clear, calm nights favour dew; cloudy nights reduce radiational cooling.