🌧️ Record September Rain on Japan's Pacific Side

❓ What happened?

According to the weather summary published by the Japan Meteorological Agency (JMA) on October 1, 2026, monthly precipitation on the Pacific side of East Japan reached 236% of the normal level in September 2026 — the highest figure since regional statistics began in 1946. The previous record was 182% in 1982, so the margin is wide. Among the 153 meteorological stations nationwide, 12 locations — concentrated in southern Kanto — set new records for highest September precipitation. Sunshine was equally extreme in the opposite direction: monthly sunshine hours on East Japan's Pacific side came to 46% of normal, the lowest since 1946 (the previous record was 54% in 1988), and both East and West Japan saw "considerably few" sunshine hours. The cause was a long-stalled autumn rain front (akisame zensen). Westerly winds were considerably stronger than normal, mainly over the sea east of Japan, making the area around Honshu prone to rising air currents. A dominant high-pressure system merged with the Pacific High stagnated to the east, while an autumn high extended from the continent, widening the north–south temperature gap over Honshu. This pressure pattern persisted throughout September, holding the autumn rain front over Honshu for a long period. Warm, humid air also kept flowing in along the rim of the Pacific High and the eastern edge of a large low-pressure area south of Japan, making the front extremely active. Typhoon No. 25 likewise tracked northeast over the sea south of Kanto along the same high-pressure rim. Looking ahead, JMA states that while the typhoon and autumn rain season continues, weather in October will change in cycles of several days nationwide with more sunny days than normal, and the chance that heavy rain and low sunshine persist on East Japan's Pacific side is small.

👥 Who is affected?

• ●Foreign residents on East Japan's Pacific side (southern Kanto, Tokai Pacific coast, etc.)
• ●Tourists and business travelers planning a trip to Japan in October
• ●People who work outdoors — delivery, construction, farming, tour guiding
• ●Households, restaurants and businesses in West Japan (especially the Pacific side) that use a lot of water
• ●Anyone living near rivers or slopes after record-breaking rainfall

🌏 Impact on foreign residents and visitors

September's record rain and lack of sunshine affected daily life across southern Kanto and beyond: laundry that would not dry, indoor humidity and mold, cancelled outings and sightseeing, and interrupted outdoor work. In October, weather nationwide is expected to change in cycles of several days with more sunny days than normal, so the practical approach is to decide trips and outings a few days at a time based on the latest forecast. Still, the typhoon and autumn rain season continues: heavy rain can suspend or delay trains and disrupt airports and expressways. In areas that received record rainfall, later rain can raise the risk around slopes and rivers, so always check the evacuation information (warning levels) issued by your local government — in a language you understand. The JMA website offers an English page and multilingual guidance, so warnings and advisories are accessible even if your Japanese is limited. Meanwhile, precipitation on West Japan's Pacific side is forecast to be below normal in October, and the chance of resolving the low rainfall seen from July to September is small. If you live in West Japan, keep an eye on municipal notices about water supply and drought as well.