General Climate in Perspective

Temperature variations in Hawaii are very minor throughout the year. There are really only 2 seasons in Hawaii: summer from May to October and winter from November to April. The annual temperature range does not exceed 9 F at any location in Hawaii below elevation of 5,000 feet. August and September are the warmest months of the year.

Except for the Kona coast of Hawaii, at elevations below 2,000 feet throughout the State winter is the season of highest average rainfall. Normally, the wettest months are from November to March. The annual rainfall contrast is largest at low elevations in the areas with low annual rainfall, and least in areas of higher annual rainfall. Cold front, Kona storms, upper level lows and tropical cyclones are four major synoptic systems can influence rainfall intensity and variability in Hawaii.

It is trade wind that determines the overall pattern of Hawaiian rainfall. In winter trade winds blow 50% of the time and the subsidence trade wind inversion occasionally disappears; in summer, trade winds and the inversion prevail for more than 90% of days. When trades wind dominate, rainfall maxima lie near 1-km MSL on windward slopes. When trade wind is weak and synoptic forcing is weak, diurnal cycle caused by land/sea breeze is the major contributor to local rainfall.