IT's cold, but they give you only about 15 minutes in the auction area. The rest of it you're waiting inside the auction holding area, which is packed with people and therefore rather warm. A light jacket probably will be enough, unless you're very sensitive to cold, and even just what you're wearing anyway is likely okay.

I did it a couple years ago. Not sure the auction is worth it. If you could drop in anytime, sure, but not worth getting there as early as you have to. I do think a trip to the market is worth it, but you can just show up later in the morning and scope it out.