Viewfinder: The Fog Days of Summer

Longtime residents know that summer along the San Mateo Coast brings gray skies and fog. Much to the chagrin of weekend vistors from over the hill, who left their home in bright sunlight, we have clouds and dampness when they arrive. Why is that?

Our moderate Mediterranean-type climate is rare in this world. Summer brings strong westerly winds, cooled by the ocean. Inland, warm air rises. The cold air along the coast, heavy and trapped by the upper warm air and the hills cannot hold the moisture which condenses in the form of low clouds and fog.

A more elegant explanation of the coastside climate can be read on the San Mateo Coast Natural History Association's web site.

Photographing the summer weather is this week's challenge.