Under which conditions is Radiation Fog most likely to form?

Radiation fog typically forms under conditions of no wind and a clear night sky. This type of fog arises when the earth's surface loses heat rapidly at night through radiation, leading to cooling of the air close to the ground. When the air temperature falls to the dew point, moisture in the air condenses into tiny water droplets, creating fog.

The absence of wind allows the cooler, denser air to settle at ground level without being mixed with warmer air aloft, thus facilitating the development of fog. A clear sky enhances radiation cooling because clouds can act as an insulating layer, reducing the amount of heat lost to the atmosphere. Therefore, the combination of still air and a clear night maximizes the potential for radiation fog formation.

In contrast, strong winds can mix the air layers and prevent the ground from cooling sufficiently. Low temperatures and high humidity are conducive to fog, but they alone don't ensure the calm conditions necessary for radiation fog. Similarly, light winds with overcast skies would likely inhibit the radiative cooling effect needed for this type of fog to form.