Of the two campgrounds available in Hawai'i Volcanoes National Park, Nāmakanipaio Campground is the larger and more commodious. This campground is located at 4,000 feet, so it does see temperatures dip into the 60s at night along with a pretty regular dose of rain. The campground is divided into halves: To the east sits 10 cabins that are available to rent through the Volcano House located in the park, and to the west sits the tent sites and restrooms. Each cabin has a double bed and two bunk beds, a picnic table, and a barbecue. Linens are provided. The tent space includes an open field where five walk-in sites are distributed and 12 individual sites with parking aprons that are ADA accessible. Sites include a picnic table and a barbecue. The picnic pavilion here is quite large, but that's a good thing when wet weather settles in here for a few days, which it frequently does. The restrooms near the tents also have a camp sink, and the restrooms near the cabins have a shower.
Nāmakanipaio Campground is located 3.3 miles west of the main entrance to the park. While this does mean that you'll want a bike or car to access the park from the campground (given the itinerary you'll have for visitation within the park), it also means you are just about a mile away from the Kīlauea Caldera as the crow flies, which is close enough to enjoy light from the volcano reflected off of the clouds.
The open design of the campground does mean that privacy will be at a premium here. Tents are all within eyesight of each other, and there is no landscaping to minimize noise. That said, you likely didn't come all the way here to hang out around the campsite, and Nāmakanipaio Campground remains a solid base camp option for your exploration of the park.