Hi Dorrie.
What a great trip to consider booking for your first one. :)
I've been twice to Cilento Coast. Only in early May though as I struggle with hot, humid weather. The first time as I remember, the weather was a little variable for the first couple of days, but then bright and sunny, although it was quite cool at night. The hotel has some lounges at the front, that do not have windows, so are open to any breezes that come through, and it did get a little chilly at night.
Having said which, the second time I went, it was very humid for the first couple of days, but then we had a terrific thunderstorm at night and after that it was beautiful.
Sorry I can't tell you about weather later on in the year, but this has proved to be a very popular trip for JY, and I am sure that there will be other Forum members that can help. If you do want anymore information I am happy to help.