What is dew?

Dew is the result of condensation on the surface of the earth. At night the earth sometimes becomes colder than the air, and when water vapor in the air touches leaves and other objects on the earth’s cold surface in the early hours of the morning, it condenses to form “dew fall”. If the earth is very cold the vapor freezes and hoar frost, instead of dew, is formed.

If, on the other hand, water vapor rising from the earth meets a leaf colder than itself, it will condense to form a different kind of dew fall.