What environmental condition is typically necessary for the formation of radiation fog?

Radiation fog typically forms under conditions of high humidity. This type of fog develops during clear nights when the ground loses heat through radiation, causing a drop in surface temperature. As the temperature decreases, the air near the ground can reach its dew point, leading to condensation and the formation of fog. High humidity allows for more moisture in the air, which is essential for the condensation process that creates fog.

Strong winds would disrupt the cooling process necessary for forming radiation fog, as they mix the air and prevent it from reaching the low temperatures needed for condensation. Large temperature fluctuations can lead to different types of fog but are not a primary cause of radiation fog specifically; it is the steady cooling without sufficient wind that facilitates it. Constant cloud cover inhibits the cooling of the ground at night, thus preventing the temperature from dropping low enough to reach the dew point, which is crucial for the development of radiation fog.