Honestly, in all my years of traveling the Caribbean, I have never had an entire rainy day on any island. Sunandfun is right. If it does rain, it's a quick afternoon shower and it's over before you know it.

If you did have the unfortunate experience of a rainy day, I would say it would be a good opportunity to do some shopping. Keep an eye on the weather and if you see a rainy day ahead, use that day to get your souvenirs and whatnot.

I have a feeling that a rain for a whole day is possible if there is a storm passing through the island. We can play in the casinos if ever we get stranded on the island because of rain. What I don't know is if the electric current will still be available when there are storms.