It honestly depends. We have done several December cruises that were beautiful and a 1/14/10 3-night that was also beautiful. However, our 1/8/11 cruise was completely different. The first 3 days were beautiful. Wednesday in Cozumel the storm hit and the harbor was closed to boats, so all excursions were cancelled. The captain steered the ship in a circle in order to be able to do the fireworks that night, though it was too windy for Mickey to zipline. Right after the characters were cleared of the stage, the ship made a hard u-turn to get back on course. We were at a tilt for so long that one CM smiled and started telling everyone to come to the portside to right the ship. Water was POURING out of the Mickey pool and the starboard side of that area was roped off because of all the standing water on deck. Deck 10 was closed off to guests that night, as well as the next day at sea. We cruised to CC with 50 knot headwinds and 20+ foot swells. The pools were closed all day. DD got seasick for the first time in 8 cruises that morning. We had Palo brunch that morning and saw several servers having problems getting to the tables. An ice bucket stand near our table fell over at one point. That was the storm that left snow in almost every state. When that cold air meets up with the warm air in the Carribean they don't mix well. Oh, and on CC we wore sweatshirts and covered up on the chairs with towels. It was very windy and low 60s/high 50s. I didn't see anyone in the water that day, though we rented the paddle boat.