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.
By contrast, Jamaica's south coast is mainly an arid region that sees little or no rain. The typical March temperature for Negril, Jamaica, on the north coast, averages between a low of 73 degrees and a high of 84 degrees, according to the Weather Channel. Expect temperatures of 55 degrees during March if you are vacationing in Jamaica's Blue Mountains. The average March rainfall in Negril is just over 2 inches. Overall, the island gets 78 inches of rain annually, mainly between May and November. The mountains receive an average of 300 inches of rain yearly, according to Visit Jamaica.