Why does fog occur during daytime?

Fog is a layer of moist air near the ground. Fog happens when there is a temperature inversion in the atmosphere. An inversion is a boundary in the air, which wind cannot easily cross . read more

If it does form in the day, it's usually because a front of cold air moves in and mixes with the warm, moist air. That cools down the water vapor in the air enough to make it condense. That's possible, but rare when the sun is out. Fog requires cold, and that usually happens at night. read more

Fog formation can occur in two ways. First, the air is cooled to the dew point which leads to the formation of fog droplets. When the air temperature is the same as the dew point temperature, condensation occurs on tiny particles floating in the air. read more

Radiation fog is most common in the fall, when nights get longer, airmasses begin to cool, and land and water surfaces that have warmed up during the summer are still evaporating alot of water into the atmosphere. read more