It may not be THE hardest in CA, but it gets my vote.....
The 18th at my current course is a downhill 211 yard par 3. Water in front, water back right, OB left and an easy to find bunker front and center. The tee is elevated at least 50 feet.
This may not seem too bad, but don't knock it until you're having a superb round and you have to stand up on that tee with the wind blowing and just try to make a par to not ruin your day.
On a similar note, I stood up there for 3 hours during a charity event trying to raise money in a "Beat the Super" closest to the pin....1/2 the guys playing were seniors and 1/2 of them didn't even want to try because....and I quote, "I've never even made it over the water on this hole." From the WHITE tees. One older gentleman LAID UP with a PW to the ladies tee 30 feet below then hit another PW to the green.
Just because it's not a 500+ yard par 4 doesn't mean it's not enough to gets your knees knocking as your last tee shot of the day!
BTW.....this is an old picture from course opening....the lake in front is filled with tall cattails now and the trees on the right are 30 ft tall.....the elevation is not represented well.