That's averages, but Norway has hot summer days too. Factor in thinner atmosphere (more UV), lower sun angles, over 20h days and you get more warmth with less average temperature.

And those buses stink like inside of a plastic factory. Never been to a plastic factory, but rode these buses. And the smell is strong even a year into use. Makes you wonder if China has same rules for carcinogenic plastic in consumer goods.

Ruter operates in and around Oslo where temperatures higher than average. Anyway some of old (diesel?) buses had broken heating and were heating even if it was warm outside. These are still improvement.