Sun Valley/Ketchum is great any time of year. But the weather is best in the summer. In fact, the cliche often heard around town is you go for the skiing but stay for the summer. For anyone who likes warm, dry climates, Sun Valley will not disappoint between June and August. Most days, it is sunny (hence the name!) with a deep blue sky. There really isn't a place as pretty. Most afternoons, the heat will break first with big, puffy clouds followed by quick thunder showers followed by cool, dry nights. Mornings are usually cool and very nice for an early hike or run. In years past, forest fires throughout Idaho's mountain regions late in the summer have left Sun Valley with a smokey scent - and sometimes smoke as well if the fire is close enough. Nonetheless,  in few  other places in the US in summer can you  almost always count on really nice weather, sunny skies, temps around 80 during the day and 50 at night, and very little rain to force you off trial, golf course or whatever your outdoor sports pursuit  (and in Sun Valley - a very healthy, outdoorsy place, you can even ice skate outside all summer long on the famous Sun Valley rink).