Sleep at Modesto Reservoir Regional Park, the full-hookup night east of town on the Waterford road. Stanislaus County takes bookings 182 days out and the hookups sit in the A, B, and C loops, so the site is the reservation you make first and the van second. Check-in is 4 p.m. Out here shore power is what runs the air conditioning through a valley night, and the loops that have it go early.
Water-skiing and hookups at Modesto Reservoir
The reservoir runs about 2,800 acres of warm irrigation water and the ski boats are on it by mid-morning, a short roll from the pads. Sort one thing before you book: Modesto Reservoir allows no pets at any time, service animals aside. With a dog in the van, book Woodward Reservoir instead, the county's sibling park up Highway 120 past Oakdale, where dogs are welcome for a few dollars a day. If the hookup loops are gone, the basic sites are first-come, first-served and put you on the same water.
Yosemite is the other reason people rent a van here, east on Highway 120 and a longer day than the reservoir. The Yosemite campervan lander has the valley campgrounds and the entrances, the California campervan hub covers the rest of the state, and RV rentals near Modesto share the same reservoir loops if you need more beds than a campervan carries.