Around Bryce Canyon National Park and the nearby Cedar Breaks National Monument area, elevations approach and surpass 9,000 feet, making for temperamental weather, intermittent and seasonal road closures due to snow, and downright cold nights well into June. The air is cooler on the rim of the canyon than it is at lower altitudes. If you choose to see Bryce Canyon in summer, you'll be visiting with the rest of the world. During these months, traffic on the main road can be crowded with cars following slow-moving RVs, so consider taking one of the park shuttle buses.
If it's solitude you're looking for, come to Bryce any time between October and March. The park is open all year long, so if you come during the cooler months you might just have a trail all to yourself.