Star Valley has a classic mountain climate: warm, short summers and long, cold winters with reliable snow. The valley sits at 1,900 metres, which means summer temperatures are pleasant rather than hot — daytime highs in July typically reach the mid-20s Celsius, with cool evenings. Winters are serious, with heavy snowfall from November through March and temperatures frequently dropping well below freezing.
Summer (June–August) is the obvious peak. Wildflowers in the surrounding hills, good fishing, hiking in the Salt River and Wyoming ranges, and the Periodic Spring at its most dramatic intermittent behaviour (late July through September is ideal). July and August can see afternoon thunderstorms — common across the mountain west and usually brief.
Autumn (September–October) is arguably the best time to visit if you're not hunting. The aspen groves on the valley slopes turn gold and orange, temperatures are crisp and clear, and the hunting crowds add a festive energy to the valley's small towns. The Periodic Spring is still performing into September. Elk rut in September produces memorable bugling in the hills.
Winter (November–March) brings Star Valley's most devoted visitors: snowmobilers. The region has hundreds of kilometres of groomed snowmobile trails, and Afton is a hub for sled rentals and guided trips. Cross-country skiing and snowshoeing are possible in Swift Creek Canyon and on forest roads. Temperatures can be brutal — pack for serious cold.
Spring (April–May) is the shoulder season: snow receding, roads wet and sometimes muddy, the Periodic Spring running continuously (not intermittently) due to high snowmelt. The valley greens up quickly in May, and bird activity is high along the Salt River.