Though I love all the Hawaiian Islands summers can be blazing hot and humid there

The hottest island in the summers is the big Island of Hawaii and the hottest place on the big island is likely Kona on the desert side of the island. However, Hilo, where I lived in 1974 was blazing and very humid when I went there to live with my wife and baby son in August 1974. When I got off the plane the heat and humidity almost did me in right then and where we were staying didn't have air conditioning with friends then either. So, because I had already had heat prostration within a year or two from working in the heat outside in above 110 degrees Fahrenheit in California I was worried whether I could adapt to these very hot and humid temperatures during the day in Hilo then. However, over time it got to be September and October and so on and it began to cool down to something I could more easily survive.

If you want to try and live on the Hawaiian islands without air conditioning the best island for this would be Kauai simply because it is the northernmost island and so the coolest year around of all the Islands. I have friends who live on Kauai and friends on the Big Island of Hawaii too but the ones on the big island would need air conditioning for the summers to be happy there. I suppose some people are adapted to living in the humid heat of the big island. One way to deal with the heat there is to live at a higher altitude because you have altitudes up to 14,000 feet on the big island and even Maui has elevations up to 10,000 feet there too. So, many people live at 2000 to 3000 feet on Maui and the big island of Hawaii to stay cooler in the summers and year around. The hottest it is going to get there on all the islands is right on the ocean where all the biggest resorts are during the summers there.