Grand Teton National Park in August

June through September is your window, but each month serves up something different. June brings wildflowers and snow-capped peaks, but also muddy trails and lingering snow at higher elevations. Some alpine lakes stay frozen into July. July and August deliver peak conditions — all trails accessible, warmest weather, and those perfect bluebird days that make you want to quit your job and become a mountain guide. But you'll share the experience with everyone else who had the same idea. Expect crowds and book accommodations months ahead. September is the sweet spot for many. Cooler temperatures, fewer crowds, and aspen trees turning gold against the granite peaks. The weather can be unpredictable — you might get snow or you might get 70-degree days. Pack for both. Winter transforms the park into a cross-country skiing and snowshoeing paradise, but most roads close and services shut down. Only the most dedicated (or crazy) visitors venture in from December to March.