I mean... I don't want to be a debbie downer it is kind of luck of the draw though. We took a vacation in the Cozumel area for New Year's (one of the stops on the Western cruise) and we were super lucky to have nice weather, but I was super nervous watching the weather because it was cold and rainy in the weeks leading up to it in December. And we picked a resort that had a heated pool and were sure glad we did because the unheated pool and ocean were COLD based on my midwestern sensibilities (granted, those of you who have posted from colder climes like Canada may have a better tolerance from cold than I do).
If weather is super important to your DH, I might suggest going a little earlier (e.g., early November) before things start to cool down. We are doing that as a precaution, but then I am like your husband and hate when whether ruins a vacay. It's also cheaper to avoid late December because of the school holidays then.