What type of cloud is fog considered to be?

Fog is classified as a type of stratus cloud. Stratus clouds form in flat, uniform layers and are typically found at low altitudes. They can cover large areas of the sky, resembling a thick, gray blanket that often leads to overcast conditions. Fog occurs when the water vapor in the air condenses into tiny water droplets that remain suspended in the air close to the ground, resulting in reduced visibility. This behavior aligns with the characteristics of stratus clouds, which are known for their low and dense formation.

The other cloud types listed, such as cirrus, cumulus, and cumulonimbus, have distinct characteristics that set them apart from fog. Cirrus clouds are high-altitude, thin, and wispy clouds. Cumulus clouds are puffy and develop vertically, often associated with fair weather but can also indicate some instability in the atmosphere. Cumulonimbus clouds are towering clouds associated with thunderstorms and severe weather. All of these differ from the flat, layered structure of stratus clouds, reinforcing why fog is classified as such.