Calm but couldn’t say ordinary, peaceful and slightly noble somehow. Serene might be a difficult word to use for non native English speakers like me. Probably I could say serene weather instead of fine but it sounds me strange. I don’t say I can’t find any proper word in my mother tongue (“うららか” might be good translation). You know it is not always easy to understand translate words.
A bit dim room open to a bright backyard tells serene afternoon.