Ya. You’re late for the Summer.
Dec 1 -> June
Jan 1 -> July
Feb 1 -> Aug
Mar 1 -> Sept
Also, don’t be afraid to use the campgrounds that don’t allow reservations. So many people want to count on there being a site nowadays that they don’t bother camping unless they have a reservation.
Well, that just means you can usually pop-in to a reservation-less campground and get a spot. I think the National Forest campgrounds are the ones that don’t take reservations.
It is pretty easy to get decent spots if you arrive on a weekday. Friday night and Saturday a.m. are the worst, though. Reserve a spot for those days or plan on hotelling it, then just “pop-in” on the weekdays.
The state campground at Pismo is kind of cool, too.