Oahu, on which Honolulu is located, is the third largest of the Hawaiian Islands. The Koolau Range, at an average elevation of 2,000 feet parallels the northeastern coast. The Waianae Mountains, somewhat higher in elevation, parallels the west coast. Honolulu International Airport , the downtown business district, the Waikiki district, and a number of the residential areas of Honolulu lie along the southern coastal plain.
The climate of Hawaii is unusually pleasant for the tropics. Its outstanding features are the persistence of the trade winds, the remarkable variability in rainfall over short distances, the sunniness of the leeward lowlands in contrast to the persistent cloudiness over nearby mountain crests, the equable temperature and the general infrequency of severe storms.
The prevailing wind throughout the year is the northeasterly trade wind, although its average frequency varies from more than 90 percent during the summer to only 50 percent in January.
Heavy mountain rainfall sustains extensive irrigation of agricultural fields and the water supply for Honolulu. Oahu is driest along the coast west of the Waianae Mountains where rainfall drops to about 20 inches a year. Daytime showers, usually light, often occur while the sun continues to shine, a phenomenon referred to locally as liquid sunshine.
The moderate temperature range is associated with the small seasonal variation in the energy received from the sun and the tempering effect of the surrounding ocean. Honolulu International Airport has recorded temperatures as high as the mid 90s and as low as the lower 50s.
Because of the trade winds, even the warmest months are usually comfortable. But when the trades diminish or give way to southerly winds, a situation known locally as kona weather, or kona storms when stormy, the humidity may become oppressively high.
Intense rains of the October through April winter season sometimes cause serious, flash flooding. Thunderstorms are infrequent and usually not intense. Hail seldom occurs, however, a small tornado or waterspout may do some damage. Only a few tropical cyclones have struck the State of Hawaii, although others have come near enough for their outlying winds, waves, clouds and rain to affect the Islands.