dewdrops

Dewdrops are small droplets of liquid water that collect on cool surfaces in the early morning as water vapor in the air condenses when the surface temperature falls to or below the dew point. They most commonly appear on grass blades, leaves, petals, spider webs, and the roofs of cars after clear, calm nights when radiative cooling to space is greatest.

Formation occurs when the air near a surface becomes saturated and the surface temperature drops due to radiative cooling. High ambient humidity and low wind help by reducing evaporation and limiting mixing with drier air. The resulting droplets are usually fractions of a millimeter to a few millimeters in diameter, forming a thin wet film on nonporous or waxy surfaces.

Dew is distinct from other moisture phenomena. It forms on surfaces at temperatures above freezing; if surface temperatures fall to 0°C or below, frost may develop instead. Fog and mist are airborne droplets, while dew remains attached to surfaces.

Dewdrops interact with light and can refract or reflect sunlight, sometimes creating a sparkling effect. They can influence leaf surface temperature and contribute to leaf wetness, which in turn can affect microclimate on the plant surface and, in some cases, pathogen dynamics.

Evaporation of dew occurs as morning temperatures rise and surfaces warm, with the rate governed by humidity, wind, temperature, and the nature of the surface. Dew is a variable, short-term feature of the diurnal water cycle, commonly observed in temperate and arid regions after clear nights.