San Francisco Bay shrouded in fog, as seen from the Marin Headlands looking east. The fog of San Francisco is a kind of sea fog, created when warm, moist air blows from the central Pacific Ocean across the cold water of the California Current, which flows just off the coast. The water is cold enough to lower the temperature of the air to the dew point, causing fog generation. In this photo, the towers of the Golden Gate Bridge can be seen poking through the fog, and the Bay Bridge is visible in the distance.Photo: Mila Zinkova