Japan’s endless summer: Record heat reshapes the nation’s seasons

The summer of 2025 has gone down as the hottest ever recorded in Japan, marking the third consecutive year of record-breaking temperatures. The nationwide average was 2.36°C higher than the historical norm, according to the Japan Meteorological Agency (JMA). On August 5, the central city of Isesaki in Gunma Prefecture registered 41.8°C, the highest temperature ever observed in the country since records began in 1898.

Autumn brings little relief

Despite the arrival of fall, the heat has not fully subsided. In Kagoshima, temperatures reached 35°C in early October, while more than 30 other locations also reported record highs for the month. JMA data showed that the number of days with temperatures above 40°C soared to 30 — nearly double the previous record of 17 days set in 2018.

Global warming drives the crisis

The scorching summer has been linked to global warming, along with unusually high sea surface temperatures in both the Pacific Ocean and the Sea of Japan. A lingering high-pressure system over the islands trapped warm, humid air throughout the season, while a northward shift in atmospheric currents amplified the effect.

In a September report, JMA’s Advisory Panel on Extreme Climatic Events stated that such temperatures “would virtually never have occurred without the influence of global warming.” The report noted that Japan’s average summer temperatures between 2023 and 2025 far exceeded projected climate models, signaling an accelerating trend.

Agriculture and fisheries under pressure

The unrelenting heat has taken a toll on Japan’s agriculture. Rice yields have dropped sharply as crops fail to withstand the prolonged heat and limited water supply. Fisheries are also feeling the strain, with traditional species migrating north in search of cooler waters, disrupting long-established fishing patterns.

Public health concerns rise

More than 100,000 people were hospitalized for heatstroke between May and early October — a 4% increase from the previous year, setting yet another record. Elderly citizens are particularly vulnerable due to the combination of high humidity and extreme temperatures.

Hotter seas, stronger typhoons

Persistently warm ocean waters around Japan have fueled more intense and longer-lasting typhoons. In recent weeks, Typhoon Nakri and Typhoon Halong struck the Izu Islands south of Tokyo, bringing winds of up to 180 km/h and torrential rainfall. Meteorologists warn that as sea surface temperatures continue to rise, future storms could become even more destructive.

A country of two seasons

Recent research indicates that Japan’s summers have lengthened by nearly three weeks between 1982 and 2023 due to rising sea temperatures — which are increasing two to three times faster than the global average. While winters remain relatively stable thanks to Arctic winds, spring and autumn are rapidly shrinking.

If current trends continue, scientists warn that within just 30 years Japan could effectively become a nation with only two seasons — summer and winter.