We went to Panama for a New Years cruise a few years back. It was fine, with nice temperatures in the 80's and sunshine. Of course that could change but still the temps should be quite pleasant even if it rains. Our biggest problem was the trade winds were really blowing and the sea time was mostly in choppy seas. Lots of sick people. I have to admit that I even got queasy a couple times. Our Captain (it was the Carnival Legend) said the trade winds were usually more prominent during that time of year. I guess so. It certainly held true for us.