The best time of year to camp in Rocky Mountain National Park is during the summer months, from late June to early September. During this time, the weather is warm and relatively dry, making it ideal for camping and outdoor activities. Additionally, the park's high-elevation roads, such as Trail Ridge Road, are typically open during this period, allowing for easier access to various areas of the park. Keep in mind that summer is also the busiest season, so reservations should be made in advance to secure a campsite. For a less crowded experience with cooler temperatures, consider camping in late May or late September.