It is known as dew water droplets deposited on the ground during the night, as a result of heat radiation of the soil to the atmosphere. This loss of heat causes soil cooling and condensation of steam from the air layer in contact with soil, on plant surfaces and other objects. The dew favors plant life and is beneficial to agriculture because soil warming graduate with evaporation. The conditions that favor the formation of dew are essentially two: a quiet atmosphere, clean and high humidity. The dew point is the right temperature to which air is saturated with moisture and resulting from this process vapor condenses on the cold surfaces. This concept is important in aviation to provide for the formation of fog.
The dew is different from the frost because it occurs when air cooling is very fast and the water vapor crystallizes. The frost is in the form of white granules and bleaching plants and objects that lie in the open until one or two meters high. However, the frost crystals formed by thin ice, originates in the coldest nights (several degrees below zero) weather with little wind.
In 1814 the work was published Essay on the dew, the London W. C. Wells, who became the first treatise on this subject.