Climate of the Hawaiian Islands

The Hawaiian Islands are home to some of the most perfect weather in the world, with temperatures across the state averaging a comfortable 72 degrees fahrenheit (22 degrees celsius). The warmest months are August and September, with January and February ranking as the coldest months, with a 5 to 8 degree fahrenheit (-15 to -13 degree celsius) difference. Although the Islands are located within the tropics, the weather is best described as subtropical, with four factors influencing the climate: (1) the Islands' location in the tropics, (2) their altitude, (3) their position in the northeast trade winds zone, and (4) the effect that the low pressure fronts have that pass generally to the north.

The Hawaiian Islands are located 2,400 miles (3,862 Kilometers) southwest of the continental United States, surrounded in the warm tropical waters of the Pacific Ocean. Hawaii's constantly pleasant weather is due in large part to the Bering Sea, with its cool waters that reach the Islands. Ocean temperatures measure 10 degrees fahrenheit (-2 degrees celsius) cooler than other Pacific regions located at the same latitude.

Steady trade winds cross thousands of miles of cool, open ocean, and are moisture laden when they strike the northeastern sides of the islands and rise due to the mountain peaks. This causes a reduction in temperature and pressure, causing the winds to drop their moisture. These areas are known as the windward sides of the Islands, with lush tree, shrubs, and tropical flowers. As the winds pass over the mountains they become much warmer and drier, descending the leeward slopes. The lack of moisture creates a climate that is arid / semi-arid.

When the trade winds stop blowing and the winds come from the south, the weather can be uncomfortably hot and humid. Referred to as "Kona winds", which bring rain to the leeward side of the islands which are dry, unlike the otherwise beautiful and lush windward side of the Islands. The exception to this are the heads of the valleys on the sheltered leeward sides of the islands which receive a great deal of rainfall.

On the Big Island of Hawaii, the huge domes of Mauna Loa and Mauna Kea tower high above the trade winds, and are large enough for local land and sea breezed to develop. It is this sea breeze which brings rain to Kona, creating the favorable conditions necessary to grow Kona's trademark coffee between the elevations of 1,000 and 2,500 feet (305 and 762 meters).

Native Hawaiians did not live on the dry plains, except along the seashore, as they did not practice common day irrigation on a large enough scale. Areas such as the Ewa Plain, located on Oahu (Ewa Beach), and the isthmus of Maui, are considered semidesert land, but thanks to modern irrigation are now home to various agricultural uses.