Karen: This is a very subjective question......since I live in the northeast of the US, I loved to sail the Caribbean in January/February to escape our winters. I've always had much better luck weather-wise sailing the eastern or southern caribbean during this timeframe. The two times we've sailed the western Caribbean, we have not had the greatest weather. The eastern and southern had temps in the 80 and 90's and was very sunny.
Mary Lou Scanlon
NCL Pride of America April 24, 2010
NCL Epic February 12, 2011
RCCL Allure of the Seas - September 18, 2011
Celebrity Eclipse - February 11, 2012:
RCCL Navigator OTS - February 9, 2013
I also live in the northeast. I don't sail in winter for a couple of reasons. I'd be afraid of cancelled flights due to blizzards, I wouldn't like to carry around winter coats on the trip, and it would be too depressing to come home to cold and snow after a week in Paradise. April and May have been best for me. Weather is usually gorgeous in the caribbean and nice here too. June is good, but hotter down there, the prices go up, and there are a lot more children, so if you are taking kids, they may enjoy it more then.Have only done one in fall, the weather was horrible, but that could have been just this year. Seems like its been bad everywhere. Happy planning. Hope this helps.
January, February and March is very iffy down here in the subtropics.
I live in Miami and today it was in the 60's (little cold for me since my blood has thinned out) this is due to the cold front from the north pushing down. The Caribbean is still in the 80's, but keep in mind if you are flying from a cold-weather snow state you might run into problems getting down here or even going home.
You can always count on April (watch out for Spring Breakers though).
But May is the best time in my opinion.
Also if you want to spend some time in the Miami/Ft. Lauderdale area, the beaches are cold as well.
I always cruise the Caribbean in May and December and have always had wonderful weather. Nice 80 degree tropical weather.
As a matter of fact I just went to the Eastern Caribbean on Jan 2-9 and the weather was perfect, but my travel mates had to head back up to New Jersey/New York and ran into snow. They were a little depressed after having a wonderful warm vacation.