We were there in Jan. last year and the weather was sunny and warm. Had a great time. Our excursion included the San Gervasio ruins and beach time. I think weather is a toss up in any month. Last year it poured when we were at Labadee, cloudy in Ocho Rios, but warm enough to climb the falls; warm and sunny in Grand Cayman and Cozumel. Windy/rainy on the sea days.
The year before the weather was warm and sunny at all our stops--Nassau, St. Thomas, San Juan and Labadee. This year it was gorgeous in San Juan, Aruba, Curacao, St. Maarten and St. Thomas (St. John excursion).
The most amazing weather was last summer in Alaska--temps in 60s and 70s, only one cloudy day (Sitka). Hardly ever needed jackets/sweatshirts. Sunny and clear in Talkeetna so we could see Mt. McKinley clear as a bell.
Bottom line--weather is hard to predict. Just go and hope for the best.
Explorer E. carib. 1/12/02
Explorer W. Carib. 1/18/03
Summit Alaska cruise/tour 8/3/03
Adventure S. carib. 2/8/04