You might have seen small drops of water on grass, plants and trees shining like pearls in the early hours of morning. These water-drops are called dew. Quite often people think that dew drops, like rain-water, fall on the earth from sky during night but this is not true.

Dew drops are formed due to condensation of water vapors. Air around us contains water vapors which we call moisture or humidity. Hot air contains more moisture as compared to cold air. During the night when the hot air comes into contact with some cold surface, water vapor present in it condenses on the cold surface in the form of droplets. These tiny drops of water are called dew drops.

The process of dew formation can be seen in a simple experiment. Take a tumbler and place it on a table. Now put some ice or ice-cooled water inside the tumbler. You will notice that after some time on the outer surface of the tumbler small drops of water have appeared. These water drops are formed by the condensation of the water vapors present in the air. Exactly in the same way when the trees, plants and grass become cold during night, the water vapors of the air condense on them in the form a dew.

The dew formation is more when the sky is clear and less when it is cloudy. When the sky is clear and the trees and plants are cooler at nights, there is more evaporation of water and hence more dew formation. But when it is cloudy, trees and plants do not get cool in the night and hence there is less dew formation. As the sun raises high in the sky, these dew drops evaporate into air.