The Stave Church and the Open Air Museum are both summer-only for visitors — open from late May to early September. The shoulder seasons in June and early September are the most pleasant: long daylight, mild weather, fewer coaches.
July is the busiest month, when the Notodden Blues Festival brings extra visitors to the area. The church holds Sunday services year-round; if you happen to be passing in winter you can still see the exterior but the interior will be closed.