They most likely form on blades of grass, branches of trees etc. Frost is a very important factor for the growing agricultural products. If the visibility is higher than those limits, the suspension is called mist . It forms when radiative cooling of a ground surface cools the overlying air below its dew point. It is more common on a clear night with light winds over marshy areas or soil saturated by a recent heavy rainfall or rapid snowmelt.
Radiation fog is usually a few meter deep and typically lasts for only a few hours after sunrise.
The duration and the thickness of the radiation fog depends on the local conditions as well as the solar heating. The fog is thick and persistent in low-lying areas such as river valleys, valley fog , and in the presence of weak rays of sun during late autumn and early winter. It forms when moist air flows upon windward side of hillsides or mountain slopes. It can persist for many days over an extensive area. It forms when relatively warm air is chilled to saturation by over-running a sufficiently cool surface.