I was talking with last night about how foggy it can get in the valley. Of course, this morning obliged quite nicely, and I got quite a few shots of it. They’re in the fog set on flickr.

Anyway, the tule’s really a rather unique thing. It can go from perfect visibilty to nothing in no time flat, which makes it interesting to drive in, and it’s all due to a quirk in California geography.

You see, most of inland California is a valley, drained by the Sacramento and San Joaquin rivers. And what happens is that there’s really only one way out of the valley — via the Delta. So during the winter, the cold air off the mountains descends and pools in the valley, and then the cold air gets trapped. Since cold air holds less moisture than warm air, the result is a thick blanket of fog.

I point out, btw, that these pictures aren’t the worst I’ve seen it. They’re just representative.