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.
The Caribbean weather region has no definable dry season, but that doesn't mean there isn't any sun. The least rainy months tend to be February/March and September/October. On average, the Caribbean weather region receives 141 inches of rain per year, with the rainiest months being July, November and December. Despite all the rain, patches of sunshine pierce through the clouds and radiate the landscape in between the scattered showers.