We went the last two weeks in August, which has the lowest chances of any snow. We stayed at Henry's Lake CG near West Yellowstone for the first half, then moved to Headwaters CG near the south entrance. Both were good. Both had electric/water/sewer hookups but no cable. Took a side trip to Cody for the rodeo show, but saw just about all the sights in the park. Three hours each way, and the show is 8pm to 10pm every day.
Two unpaved roads we didn't use because it was late in the day: Blacktail Plateau Drive, and the road from Mammoth Hot Springs to the North Entrance.
The traffic was always heavy between Old Faithful and Madison.
The short summer is road repair season.
