Radiation fog forms during clear nights when the ground loses heat through radiation. As the surface cools, the air close to the ground also cools, leading to condensation of moisture in the air. This process creates a thick layer of fog, often seen in valleys or low-lying areas. Typically occurring in late fall and winter, radiation fog can reduce visibility significantly. It usually dissipates shortly after sunrise as the sun warms the ground and the air, causing the fog to evaporate. This type of fog is common in many regions, especially where humidity levels are high.