Anxiously waiting to hear about weather too!
We usually go in February and do jeans and a short sleeve t-shirt and a jacket or sweater later in the evening... only a few times had rain and used rain jackets (also beign from the Pacific Northwest rain doesn't scare us!)
But last year we went in December and it was 80! I was miserable because we just didn't plan for such summier weather. I also was hoping for a cooler more "christmasy" feeling...
I am thinking about a mix of shorts, capris, with sweaters and sweatshirts.