One day last week, I left downtown Lafayette--the town east of Berkeley where I live--at about 11:00 AM after walking the dog and running a bunch of errands. It was a perfect day in Lafayette: clear, sunny, a nice breeze blowing from the west, and the temperature in the mid-70s headed for the high 70s. I drove west toward my office in Berkeley proper. I crested a hill. And there it was: the fog wall--700 feet tall, with its feet on the east side of the Berkeley Hills. As I watched, I could see streamers of it blown by the wind to the east extend their tentacles, and then vanish as the warm sun evaporated them.

I passed into the fog wall. The sun vanished. The temperature dropped by a good 15 degrees. I hastily closed the sunroof as I felt the fog drip and saw the drops it spattered on the windshield.

It was a cold grey day in Berkeley.