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.
Jamaica Weather in September: Still Hot & Still Humid. Jamaica weather in September is very much like weather in August with one notable exception... ...the possibility of more rain during this month. However, the days are still hot, still humid, and still filled with long hours of daylight.