Hawaiian Islands have a wet and a dry side
Many are surprised that islands as small as Hawaii's vary so much in rainfall from one side to the other. For example, Hilo on the Big Island receives an average of 125 inches of rain a year while Kawaihae (which is only 50 miles away) receives an average of 10 inches per year. Part of this is because Hawaii lies in the path of the trade winds. As the winds blow across open ocean for miles the air picks up moisture. When the warm moist air strikes the Island's mountains it is forced upward. As the air is cooled it can no longer hold the moisture and it is dropped as rain. After the winds pass the summit of the mountains and descends it is warmed and there is little rain on the leeward side of the Islands. Most tourist resorts are located on the leeward or dry side of the Islands such as Honolulu on Oahu, Kona on the Big Island, Ka'anapali on Maui, and Po'ipu on Kauai.