The highest temperature in Sapporo is around 18 degrees Celsius, and the warmth of the season ahead continues. It seems that you can spend comfortably in a thin jacket during the day.
Naha will rise to nearly 30 degrees Celsius and the heat will continue. Well-ventilated and thin clothes are likely to play an active role. Take measures once morest heat stroke, such as taking water diligently.
Tenki.jp has areas other than the above figureApparel IndexThere is also. People feel the heat and cold differently, so this is just a guide, but please use it as a reference.