 At one extreme, the annual rainfall averages to or less in leeward coastal areas, such as the shoreline from Maalaea Bay to Kaupo, and near the summit of Haleakalā.At the other extreme, the annual average rainfall exceeds along the lower windward slopes of Haleakalā, particularly along the Hāna Highway.Big Bog, a spot on the edge of Haleakala National Park overlooking Hana at about 5,400 feet elevation had an estimated mean annual rainfall of 404.4 inches over the 30-year period of 1978 to 2007.