Unless you visit during November, December or January, the weather is probably going to be hot. You're also going to be walking around a lot, getting very sweaty in places it's not particularly pleasant to be sweaty. You'll be amazed at how much better pulling on a fresh pair of drawers at 6 p.m. can make you feel.
On a related note — and this one goes out mostly to the men — you're going to be tempted to leave all your underwear at home and spend your trip going commando. It seems like such a Las Vegas thing to do. Don't do it. I won't go into detail, but I'll just assure you it's a bad idea. Run a web search for the term "gaulding" and everything will become clear.
