Weather patterns in the Keys differ greatly from those in Miami. Clouds rarely collect over the Keys as it does over the larger land masses on mainland South Florida. Rainstorms are usually brief. If you are unsure about the weather, phone the captain an hour or less before the cruise or check the following links for Islamorada, Florida.
(Links will open in new browser window.) 

Key West Forecast provided by floridaforecast.com

www.wunderground.com

AccuWeather.com - 15 Day Weather Forecast for Islamorada, FL

Tide Location Selection for the Florida Keys Area
(Select choice #3, Indian Key to Conch Key, then select the specific location you want tide information for. Scroll to the bottom and select the dates, then click "Get Tides")