I know this was a long time ago that you asked it but I'll share my experience! I sailed out of Baltimore on NYE in 2017 and it was quite cold. According to historic weather charts, so I can't exaggerate, it was -13 celsius when we left. The cold air creeped in through the balcony glass and the room was chilly. We couldn't watch movies on deck or sit outside or anything like that. After two chilly days at sea, we reached Port Canaveral where the temp was +5C, with storm warnings, wind warnings and marine warnings in place - our excursion was canceled and we stayed on the ship watching the palm trees bend over horizontal to the ground lol
In Nassau we got off the ship in sweatshirts but took them off for about an hour after we walked to the zoo. It was apparently 18C.
I only took one sweatshirt and my child knocked a cup of coffee on me on embarkation day 🤪so I have decided that this time I'm anticipating wearing jeans the entire time, and having enough sweatshirts for every day, and plenty of shawls and coverups for dinner. And maybe keep my winter coat nearby for hot tea on the balcony hahaha. I sure hope we have a warmer time than back then, though!