Depending on the type of winter they have been having, MT can be cold and damp in early June. We rode south out of Missoula at the end of June of '11. Hit the first stretch of nice weather all summer. The week before we arrived, snow was predicted in several areas. The day we landed at MSO there was about 2" of rain in Darby, where we would pass through the next day. A few weeks before we left I found a CGOB journal where the author had to get a ride over the pass between Ennis and Virginia City due to heavy snow. Even though we lucked out with precipitation, we still had some sub-40 nights.