No lights ... but wipers on? Not quite illegal.
The neighborhood café very helpfully hung a framed placard (like Employee of the Month) that informed me that there's a new California law making it illegal to drive in inclement conditions without your lights on.
via voltos' photos
But there's been some confusion about when it goes into effect. The sign said January but that seems to be a common misconception (snopes.com) along with the belief that the law somehow ties lights to windshield wiper activity. The wiper constraint isn't correct, and the law actually begins July 1st, 2005.
Actually, huh, come to think of it ... how are we supposed to find out about new laws we didn't vote on? I suppose (and I think I'm only half-joking) that it'd be nice if they were in a feed. :)