6 months in advance.

For anyone with small trailers (under 16'), you can also reserve a primitive camping site; you will need to unhook and park nest to your trailer. It's $22, no generators allowed. I just got 2 nights at one of the tent sites, and same at White Tank.

They open the reservation window at 8 am 6 months before the date. You have to have your lucky stars aligned to get a spot though. We had two computers going, hitting refresh over and over and over. After about a week of doing it every single morning, we finally got something for March. It’s pretty frustrating. Especially when you arrive and find people staying there for 6 months. (One guy even got two separate spots for two RVs for 6 months). It doesn’t seem right.

Reservations for Maricopa County Parks can be made up to six months in advance.

You might get lucky and find something last minute. We did at Usery, a nearby park.. Just look online at Maricopa Co Parks