Peak Season: June to August; December to March
Larger cities like Boise are busy all year, but resort spots like Sun Valley and Coeur d’Alene have sharp spikes—during peak season and holiday weekends, hotels and restaurants are booked months in advance and the beaches and camping areas can be crowded. The weather is moderate and typically dry, but temperatures do fluctuate. Most of the state has snowy winters and short, warm summers with cool nights.
Off Season: April and May
Spring is probably the calmest time of year, particularly in Sun Valley, when thawing snows hamper most outdoor play. In some of the northernmost parts of the state, late winter and early spring can be particularly gray and rainy, with overcast skies lasting until summer. But this is the best time for white-water rafting and kayaking as melting snow swells rivers to capacity.
Shoulder Season: September to November
Locals in Sun Valley call this the "slack" season. But it's the time to find great deals on otherwise expensive hotels and enjoy spectacular scenery without the crowds. Similarly, Coeur d’Alene is still charming but much more economical than during the busy summers.