We have sailed a few times in January and February and found the water to be very chilly. Our most recent cruises were in early January (Magic) and it was rainy, windy and cold (60's) We did not swim. We did not even leave the ship until about noon, took some photos and then had lunch and went back on the ship.
In February (Dream) the weather was warmer on air temps...but the water was still colder than we like.
Keep in mind, we are Floridians and to us anything lower than 70 is "brisk" lol If you are coming from a Northern place that has snow when you leave...the air temps and even water temps will be no big deal for you though.
We have also sailed in April, May, June, September, October, November and December...the best air and water temps were in September and October with a close runner up of November. We also like May and June a lot for the water temps on CC.
January and February seem to have some issues docking at CC if the winds and water conditions are wrong. It really all depends.