The full season runs roughly from Memorial Day in late May to Indigenous Peoples' Day in mid-October. July and August are warm, busy, and book up months ahead; September is the locals' favourite — the crowds drop, the water is still swimmable, and the colour begins to turn in the maples.
Early October is peak foliage in Acadia and the second-busiest stretch of the year, with weekend traffic on Route 3 backing up onto the bridge. November through April most restaurants and inns close and the town goes quiet — bracing if you want it that way, but plan ahead.