Ryanair offer travel insurance policies as an add on to a flight booking, or they can also be purchased as stand-alone products. Ryanair travel insurance is offered in two levels, so you can choose the option that's right for you and your wallet.
Jamaica's rainy season coincides with ours here in Florida (I am in the Tampa area) for the most part. We have anywhere from 30-50% chance of rain daily until hurricane season is over. I didn't mean you have rain every day, all day from May to December in Jamaica, but I assume it is a lot like here in Florida.
October is the midst of the Caribbean's rainy season. This is the rainiest month of the year for many places, including Jamaica, Cayman Islands and the US Virgin Islands. Hurricanes and Storms Bad weather during October most often occurs around eastern Cuba and the Cayman Islands.