All this talk about hair.... I always shower in the morning primarily because my fine, blond hair are the very definition of very bad "morning hair" when I get up (especially if it's hot and I have been sweating). So I always wash it, and always, always blow dry my hair in the morning or else it looks dowdy. Unfortunately my hair won't grow long enough to gather in the back, so that's not an option for hiding a bad hair day.
My hair can really annoy me
Oh, and if have a heatwave (a Scandinavian one that is: +25 C), I might feel the need to wash a bit in the evening.