Yakushima’s Climate
There is a famous saying that it rains 35 days a month in Yakushima. Due to its topography and the Kuroshio Current, the island receives the most rainfall in Japan, creating verdant forests, gushing rivers, and tumbling waterfalls.
The Wettest Place in Japan
The high mountains bring heavy rainfall to the interior of Yakushima. The island is located along the Kuroshio Current, which transports warm water northward to Japan from the Philippines. Warm vapor rising from the ocean comes in contact with Yakushima’s peaks, several of which are over 1,800 meters high. The vapor condenses and cools as it continues to rise, forming clouds and bringing precipitation. Whereas the coastal town of Nagata recorded average annual rainfall of 1,377 millimeters, the central areas of Kosugidani and Mt. Miyanoura recorded average more than double those amounts, with 5,693 and 6,960 millimeters respectively in 2017.
Rainfall in the eastern part of Yakushima is heavier than in the south and west due to warm low-pressure fronts and typhoons that pass over the island from the southeast. Yakushima is located at a turning point on typhoon tracks, with typhoons forming with the greatest frequency in the Pacific from July to October. The island receives around half of its annual precipitation between May and August due to the East Asian rainy season.
Shiratani Unsuikyo Ravine
Abundant rain and high humidity allow many varieties of moss to grow at Shiratani Unsuikyo Ravine. Hiking trails traverse a misty, moss-covered primeval forest that is said to have inspired the scenery in the Studio Ghibli animated film Princess Mononoke. Around 690 of the 1,700 moss species in Japan thrive in the damp climate of Yakushima. After a rainfall, the rainwater-storing moss is revitalized and creates a spectacle of varying shades of green. Peat mosses have cells that absorb water 16 to 26 times their weight, and turn white if they are too dry. Mosses of the Meteoriaceae family found at high altitudes are longer and hang from tree branches like curtains. The Shiratani River feeds the ravine with clear mountain water.
Getting there: By car, about 45 minutes from Anbo Port, 22 minutes from Miyanoura Port or 32 minutes from Yakushima Airport
Ohko-no-taki Waterfall
Ohko-no-taki Waterfall is the largest waterfall in Yakushima, plunging 88 meters. The cascade becomes even more dynamic after a heavy rain. Drinking water from the nearby Ohko Spring is said to bring good health.
Getting there: By car, about 53 minutes from Anbo Port, 68 minutes from Miyanoura Port, or 62 minutes from Yakushima Airport
Hydroelectric Power Generation
Yakushima’s abundant water supply is harnessed to generate electricity. Yakushima Denko, a private company, operates three hydroelectric power plants, and Kyushu Electric Power, also private, owns one such plant. Hydroelectric power provides almost all the electricity used on the island; a thermal power plant owned by Yakushima Denko is used only in emergencies and when the hydroelectric plants are under maintenance.
From Subtropical to Cold Climates
The varied topography of Yakushima creates a range of climates, from subtropical on the coast to subarctic in the mountains. The coastal areas are mild even in the winter, but the Okudake mountain range, with altitudes around 2,000 meters, is cold year-round and can get three to six meters of snow. Different vegetation grows at different altitudes, with a total of some 1,900 species of plants found in the island’s ecosystem. On the same winter day, there may be snow on the mountains and hibiscus flowers blooming near the coast.
