I think all three work. "Perfect" would also work. The thing I find awkward is the season vs.
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AvangiThe thing I find awkward is the season vs. the night.Please elaborate. How is that awkward? I think it's very picturesque. When I think "Halloween season", images of full moons, cemeteries and dark, foggy nights immediately come to mind.
Grammar GeekI like Ann's befitting the best, and appropriate the second best.So, in other words, "how befitting the Halloween season, he thought to himself (...)" would be your first choice?