The Weather is quite an uncertainty and you should wait until that day to get to know the wether for sure depending upon what you are doing because the weather usually depends upon what elevation you are at that day. So check the weather daily it changes all the time anywhere you are.
There are many Land forms here o this island and in this park Such as Volcanoes, Hills, and Ocean this park is connected to the ocean so that as well as elevation definately effects the weather.