Eastern Idaho in September

June through September delivers your weather window. July and August see temperatures hit 80°F in the valleys, perfect for hiking and fishing. But crowds descend on Yellowstone, so book accommodations early. September brings my favorite conditions – cool mornings, warm afternoons, and aspen trees turning gold across the Caribou Range. June can be muddy as snowpack melts, but wildflower displays in Teton Valley rival anywhere in the Rockies. Winter transforms the region into a powder paradise. Grand Targhee averages 500 inches annually, and backcountry skiing in the Tetons draws experts from around the world. Temperatures drop to -20°F regularly, and some mountain passes close November through April. Spring exists for about three weeks in May – everything melts at once, creating impressive waterfalls and impassable mud.