Since you're in Cali, I'd take a wild guess it's a Gopher Snake.
By the picture, it's pretty hard to tell but i'd say it's a Gopher by the girth, patterns, and how the head of the snake is a darker than the body.
Also Gofers are wild all over California, I find them all the time out here in the Bay Area.
I'm not too good with snakes, so don't take my advice too much lol. Hopefully another member can correct me / agree with me
-Gabe