I used to wear shorts year round. My teachers frequently said I was crazy (I think they really wanted to say stupid, but they couldn't cuz of them being a teacher and all). I live in Texas, but it can still get fairly cold here (there's usually at least a few days where it drops down to ~10-20 degrees) between November-February/March-ish.
I haven't actually bought clothes in a very long time now (so hard to find pants/shorts that I can tolerate, much less like) and I don't have any shorts that fit me, so I wear pants year round now.. With the exception of this one pair my friend gave that has zippers at the knees and can be pants or shorts.