Thursday, September 15, 2011

Hawaii Island’s climate zone diversity

The island of Hawaii has the climatic diversity you would find on a large continent. The many climates are due to the high elevations of Mauna Kea and Mauna Loa, the persistent northeasterly trade winds, and localized wind circulation that creates micro-climates.

In the 1900’s a climatologist Vladimir Köppen classified the world’s climates into five zones based on temperature and rainfall: Tropical, Arid, Temperate, Cold-Continental, and Arctic. Hawaii island has four of the five the Köppen zones, all except for Cold-Continental. Climatologists have since delineated sub-zones for each of the Köppen zones, and the Big Island has ten of the most common climate sub-zones.
The summits of Mauna Kea and Mauna Loa, above the tree line at 9800 feet above sea level (3000 m), have peri-glacial Arctic climates where the soil is permanently frozen. Over 2/3 of the island is in one of the three Temperate zones (zones 7, 8, and 9 on the map) at altitudes below 9800 feet (3000 m). From altitudes of 8000 to 9800 feet (2500- 3000 m) are Temperate zones with cool temperatures and a dry summer. From altitudes of 6500 to 8000 feet (2000-2500m) is a Temperate zone with warm temperatures and dry summers. This zone extends down the slopes of the volcano, on the leeward side of Kohala, and south of Waimea town. From 1600 to 6500 feet (500-2000 m) is a large Temperate zone with warm temperatures and year round rainfall. The towns of Volcano and Waimea are in this climate zone.

The most populated areas of the island, from sea level to 1600 feet (500 m), are in one of the four humid Tropical climate sub-zones with varying amounts of rainfall. The windward side from Hawi to Hilo and Puna to Kalapana has a continuously wet climate with no dry season. There is a small area along the Hamakua coast that is in a Tropical monsoon sub-climate zone with high annual rain fall and a very short dry season. Areas between the windward (east) and leeward (west) sides of the island from Kalapana to Pahala all the way to Oceanview, have a Tropical dry summer climate. Outside of Hawaii, this rare Tropical climate only exists in parts southern India and Sri Lanka.

The Kona coast on the leeward side of the island is the only area in the Hawaiian islands with a Tropical zone that has a wet summer and a dry winter. This dry winter zone extends from sea level to an altitude of 1300 feet (400 m) where the climate changes to continuously wet. Above 1600 feet (500m), the climate changes yet again to warm Temperate, but still continuously wet. Newcomers to Kona expecting the same warm, sunny weather they had during a winter holiday in a Kailua-Kona hotel are often disappointed with the continuous rain at their new house just 1500 feet above Kailua bay.

On the Kohala coast, the huge volcanoes bar the rain clouds and create a desert. Kaiwaihae is the driest place in the State of Hawaii with only about 7 inches (190 mm) of rain a year. At sea level there is a true arid desert with a semi-arid region above it at higher elevations. All the big resorts on the island of Hawaii are located in this desert area guaranteeing visitors a sunny and warm vacation year round. Many visitors come to think that the hot, dry, sunny climate of the resort area is the norm for the island, however only 445 full time residents live in this desert climate zone. Most of the island’s population live in one of the Tropical climate sub-zones that get from 60 to 300 inches of rain a year.

The large differences in weather on the Big Island can be hard to grasp. For example, Phoenix, Arizona, generally considered a desert, gets an average rainfall of 8 inches a year. Eugene, Oregon, about 940 miles away, gets an average of 50 inches of rain a year. These two cities are a thousand miles apart and not surprisingly, are in very different climate zones with a net difference in average rainfall of about 42 inches. In contrast, the “dry” areas of Hilo with an average 130 inches of rain a year are only 60 miles away from the Kawaihae desert area, a difference in average rainfall of 125 inches a year within an hours’ drive. The wetter parts of Hilo at elevations of about 1200 to 2000 feet can get over 280 inches of rain in a year. Within 60 miles, you can choose a site with rainfall close to the amount in Death Valley or rainfall five times greater than the “rainy” Pacific Northwest and everything in between.

You can read more about finding the right climate in Hawaii and other topics helpful to know before buying a home in Hawaii in our new book: Your Ideal Hawaii Home

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