The leeward side, especially of the larger volcanoes, is sheltered from the predominate weather pattern in Hawaii: trade winds from the northeast. Sometimes, the wind changes direction. In the winter, low pressure systems can form near the islands, which draw warm, moist air up from equatorial regions. These can often cause downpours and flash flooding all over the island. The windward (Koolau) side gets soaked as well as the leeward (Kona) side.Summers in the leeward sides are very often hot and dry in the summer. For example, Diamond Head (also known as Leahi) in Honolulu turns brown in the summer and turns green after its first good soaking of the winter. I lived in Kaunakakai, Molokai in the summer of 2006, when the town (in the rainshadow of the east Molokai volcano) got a grand total of 7/100 of an inch of precipitation between May and October.
（参考信息：我问这个外国人的问题是：在夏威夷是不是背风处在任何时候都没有雨？）