All excellent responses to your question. Another recommendation to go in September versus May/June. Out here in the Rockies, we also have mud season, which corresponds with May/June and in to July depending on elevation. Mud season is that time when the snow is melting, sometimes rapidly, and there is mud everywhere. This is particularly true of NP/USFS campgrounds, where there will be snow on the ground in May/June. Commercial CG/RV parks cope with it better, so it won't be as bad in those locales. Tracking in mud inside one's trailer/RV can be a chore, so leave shoes/boots somewhere outside, easily accessible. Mud season will also cause many trails/hikes to not really be doable, much less pleasant. September will be more pleasant, as the trails/CGs have had all summer to dry out. Yes, September can see snow, but early in the season it is frequently light and fluffy vs heavy and wet. And it usually melts quickly in early September.
