We also cruised this past Jan. on the Wonder. The weather was nice for us. It was warm enough to be comfortable in summer clothes, but it wasn't anything too hot. The only time we had bad weather was the morning that we disembarked, and it was rainy and cold then. The water had gotten rough, and I remember thinking that I felt sorry for the next group going out.
If we ever get to book again, I think January will definitely be one of out dates to pick from!