I concur with last speaker
(Itīs the reason IFR for light a/c is not big over here)
Summer is better than winter, and the west coast south of Trondheim is worse than the rest. If you are apprehensive about the weather, making sure the cloud base is higher then ALL the terrain along your route, your fine. (Flying in valleys that are "capped" with cloud is not all that nice if you are new to mountain flying, and apart from the area in the south east around Oslo mountains are the norm)