The formation of dewdrops is dependent on radiation cooling. During clear nights, the earth`s surface loses heat in the form of radiation which cools the surface. When the surface cools below the dew point, which is the temperature below which water droplets begin to condense and dew can form, moisture is gathered from the surrounding air to form dew on the cool surface.

Option 1 is incorrect because clouds do not absorb the radiation released from the Earth`s surface, rather they block it.

Option 3 denies the fact that it`s warmer on cloudy nights. The presence of clouds at night help to keep temperatures warmer because they re-emit radiation back to the surface, preventing it from cooling to the dew point.

Option 4 is incorrect because occurrence of dew has no correlation with wind.

Option 2 is the correct answer. The clouds reflect back the Earth`s radiation which prevents the ground from cooling down sufficiently to the dew point which hinders the formation of dewdrops.