One of the members of my group saw a GM at the local game store running his game in a suit a few weeks ago. It was a brief anecdote, and not even that interesting. However, last Sunday I showed up to run my Exalted game in normal shorts and a tshirt, and was given a good pile of shit about not wearing a suit.
So I think that means I have to show up in a suit today. The ideal solution would be to wait several months and do it then, but I don't think I will remember it that long.
I also doubt that the suit will stay on for the whole game, because it's summer and the hosts don't have AC.