What should I pay attention to when I take a cruise to Okinawa, Japan in early July? How's the weather?

I just came back from Okinawa recently, and the weather is similar to that in the south of China. Take the northern valley area in central Okinawa as an example. The highest temperature in the daytime is about 20 degrees Celsius, and the lowest temperature is about 15 degrees. It will be even hotter in July. However, Okinawa is a long and narrow island, with tens of kilometers at the north and south ends, so the temperature in the north of Minhang City and the north of the headquarters will drop by about 10 degrees, while in the south. www.nanhutravel.com/youlun