That depends on you. Spring brings snowmelt and mud to our mountain towns and early green to valley communities. Rivers usually run big and muddy from late May through July. All this means that in early summer, the fishing isn't generally too hot, the mosquitos are swarming, and the high country is not easily reachable due to slow snowmelt and swollen, difficult creek crossings. However, the weather is pleasantly cool, and lower-elevation wildflower meadows can be breathtaking.
Wildflowers burst out in the higher elevations.
Down low, farmers' markets begin to fill with local produce. Recreational gardeners watch the news for frost warnings starting around the first week of September. Fall means stable high-pressure systems which bring cool, clear days bracketed by chilly nights. Lower valleys are still enjoying fall weather as the mountain towns slip into winter. Up in Grand Teton and Yellowstone parks, fall usually means sweater weather until the sun sets.