A fog is most likely to develop when a

A fog is most likely to develop when warm moist wind blows over a cold current. Fogs are formed when the air near the surface of the earth cools to its dew point, causing water vapor in the air to condense into tiny water droplets. This often happens when warm moist air encounters a cold surface, such as a cold ocean current or a cold front moving in. As the warm air cools near the cold surface, the water vapor in the air condenses into tiny water droplets, forming fog. In the case of warm moist wind blowing over a cold current, the warm moist air from the land or ocean meets the cold current, which causes the air to cool rapidly and form a fog.