Dew is water in the form of small droplets that appears on thin, exposed surfaces such as grass, leaves, car roofs, or railings, typically in the early morning or evening. It forms through condensation when the surface temperature cools down to or below the dew point-the temperature at which the air's moisture condenses into liquid water. This cooling usually occurs due to radiative heat loss to the open sky during clear, calm nights. As the surface cools, atmospheric water vapor condenses faster than it evaporates, resulting in the formation of dew droplets

. If the temperature drops below freezing, dew forms as ice crystals known as frost. Dew is most common on surfaces that do not conduct heat well from the ground, making grass and car roofs common sites for dew formation

. The dew point is a key concept in understanding dew; it is the temperature at which air must be cooled for condensation to occur, dependent on humidity and pressure

. Dew plays an important ecological role by providing moisture for plants and animals, especially in arid regions, and can even be harvested as a water source under the right conditions