Answer to Question #75 in Molecular Physics | Thermodynamics for supertony
Why is the fog formed in the chilly days over unfrozen patches of water?
These are so-called fogs of evaporation - they are the fumes from the warmer evaporating surface (water temperature is always above zero, while the air above the water may be significantly less than zero) into the cold air over the ponds and wet land areas. Adjacent to the water, cooled air has a lower temperature than water. Therefore, the additional amount of steam from the warm water surface in the cold air evaporates. As a result a mist of evaporation is created.