I don't know why more people don't think to do this.
Maybe because people have school in fall, or because you can't rely on going outside for it all the time.

My fiance and I are going for it though. I mean, let's look at the positive sides.
You're not sweating during the ceremony. Small kids aren't so energetic. Fall's a lot nicer looking outside with all the gold and crap.
I have a cousin that did likewise, it was pants.
Of course, this is also my second attempt at announcing the big news on DF, it's just that last time i did it in off topic and it got hijacked real quick and turned into some sorta sexual thread (imagine that).