Kumamoto Prefecture is located in the Kyushu region of Japan, with Kumamoto City as its capital. In the former provincial system, it was part of the "Higo Province." The area is rich in nature, facing the Ariake Sea, the Yatsushiro Sea (also known as the Shiranui Sea), and the East China Sea. Kumamoto has the second-largest population in Kyushu, following Fukuoka Prefecture.
Geography and Terrain
Kumamoto Prefecture lies in the central part of Kyushu's main island. It shares land borders with Fukuoka, Oita, Miyazaki, and Kagoshima Prefectures, and is also adjacent to Nagasaki Prefecture across the sea. To the east lies Mount Aso, a globally renowned volcano, along with the Aso Caldera, the second largest caldera in Japan. The Kyushu Mountain Range extends through the region, forming rugged mountainous terrain. On the other hand, the western part of the prefecture features the Kumamoto Plain, which faces the Ariake Sea. The Yatsushiro Plain and the Ashikita region exhibit ria coastlines. The Uto Peninsula, jutting into the Yatsushiro Sea (Shiranui Sea), connects to the Amakusa Islands.
Kumamoto City, the prefectural capital, is home to approximately 700,000 people and is notable for sourcing all of its tap water from groundwater—an urban structure that is rare even by global standards.
Climate
Kumamoto Prefecture falls under the Pacific climate zone, characterized by a mild climate with significant temperature differences between summer and winter. Each region within the prefecture also exhibits its own distinct climatic features.
Kumamoto Region (around Kumamoto City)
The average annual temperature in Kumamoto City is 17.2°C. The Kumamoto Plain has a basin-like topography, giving it characteristics of an inland climate. It often experiences midsummer days (over 30°C) from May to October. In 2005, a record of 106 midsummer days was observed. The high humidity and "Higo no Yunagi"—a phenomenon where winds stop in the evening—intensify the oppressive summer heat. Rainfall is concentrated during the rainy season, with about 40% of the annual precipitation falling in June and July. Snowfall in winter is minimal, but temperatures can drop significantly. In January, the number of winter days (where the daily low is below 0°C) exceeds 10 on average.
Aso Region
Centered around Mount Aso, this mountainous region is one of the coldest areas in Kyushu. Snow is frequent in winter, and snow accumulation is common. The average low temperature in January is −2.7°C, and it can drop close to −15°C during cold waves. Summers are cool, and temperatures at the summit of Mount Aso rarely reach 30°C. Rainfall is abundant, exceeding 3,000 mm annually.
Amakusa and Ashikita Region
Surrounded by the sea, this region has a maritime climate with mild temperature fluctuations throughout the year. Even in winter, the average low temperatures remain between 2°C and 5°C, and annual precipitation is around 2,000 mm.
Kuma Region (Hitoyoshi Basin)
This inland basin area experiences an inland climate with large temperature differences between day and night. Summers can be extremely hot, while winters often fall below freezing, making it a cold region. The annual precipitation is approximately 2,400 mm, making it relatively rainy.
Kumamoto Prefecture features a diverse landscape—including volcanoes, mountains, seas, and basins—resulting in a wide range of climatic conditions. Each area has its own unique natural environment and climate, giving rise to diverse lifestyles and cultures.
