🇯🇵Japan

Japan spans 24°27′–45°33′N as an East Asian island nation (approximately 377,975 km²) comprising four main islands — Hokkaidō, Honshū, Shikoku, Kyūshū — plus the Ryūkyū chain (Okinawa) and roughly 14,000 smaller islands stretching 3,000 km north–south. Intensely volcanic and mountainous, the landscape features the Japanese Alps on Honshū, Mount Fuji (3,776 m, the highest peak), and active stratovolcanoes like Sakurajima, Asama, and Aso.

This extraordinary topography produces a complete climate spectrum — humid continental (Dfb / Dfa) in Hokkaidō and northern Honshū with heavy lake-effect snow on the Sea-of-Japan coast, humid subtropical (Cfa) across most of central and southern Honshū, Shikoku, and Kyūshū, tropical rainforest (Af) and tropical monsoon (Am) in the Ryūkyūs, and tundra/alpine (ET / EF) on the highest Japanese Alps and Mount Fuji summit.

Tokyo averages 6°C in January and 27°C in August with 1,530 mm rainfall and a marked tsuyu rainy season June–July plus the autumn typhoon season. Sapporo records −3°C in January and 21°C in August with 1,150 mm and heavy lake-effect snow (approximately 6 m annually). Niigata on the Sea-of-Japan coast averages 3°C in January and 26°C in August with 1,800 mm — among the snowiest cities on Earth.

Japan experiences major typhoons including Vera (September 1959, roughly 5,000 deaths), Tip (1979 — the strongest tropical cyclone ever recorded), and Hagibis (October 2019). The July 2018 western Japan floods killed approximately 225 people, and August 2020 saw a record 41.1°C at Hamamatsu.

Our archive covers 2 Japanese cities with daily ERA5 reanalysis data going back to 1940. The warmest July averages occur in Tokyo, around 28.7°C, while Tokyo records the coldest January nights near 0.3°C. Comparing the last decade against the 1940–1970 baseline, mean temperatures across these cities have risen by about 1.8°C.1°C at Hamamatsu, intensifying typhoon impacts like Hagibis 2019, the catastrophic July 2018 western Japan floods, and accelerating heat-related mortality.