Anywhere in that country could be a zoo on the fourth, especially near Hat creek. or the Pit River. In addition, boon docking could be a problem because of the heat wind and grass-pay attention to red flag warnings and if you think you have found a neat place, call the proper land manager to get the scoop. All that said, water, fishing, no/few people, try Butte Creek Prim CG (few People), it has a creek and it is on the way into Lassen NP from HW 44, so maybe camp at the cg, then drive in to Butte Lake and fish-been hearing good fishing things about that place.. Lava Beds NM is a neat place too, can try for the Medicine Lake area but will also be busy, but you might luck out there-lot's of places to play!
Try to BLM cg (Pit Power House) on the Pit River off of 299, could be busy but a nice place. Head up to my old stomping grounds, first hit Ash Creek FS CG near Aden off of 299 about 10 miles-great fly fishing-busy, head north on 139 to the Devils .Garden area on the Modoc, start at Res F ( hw 139) NW of Canby, then Res C, then north to Janes Res, then south to Alturas-lot's of water, fish and a good chance that you might find a place to dry camp either at one the res or at one of the many smaller lakes and res. scattered around that country. RED Flag Warning. Warners should be full of people, but take a trip on Fandango pass (from HW 395) to Fort Bidwell. Here is another thought-Rocky point prim CG on the North end of Eagle Lake, water, plants and wildlife seems to be coming back after all these years of drought. Fishing is okay, but a boat is a good idea-there is a good BLM cg also on the north end, but keep away from the fs CG's on the south end-will be a zoo. That is enough for now, hope you have a nice break-in, but the fourth could be interesting up there! Drop a line if you want more details.
Smoke