Tokyo’s air feels dense enough to lean against by the end of July. While elderly residents loiter near convenience stores for the momentary respite of automatic sliding doors releasing conditioned air, office workers exit Shimbashi Station and fan themselves with folded documents. This is not unusual anymore. The persistence is what seems different. At sunset, the heat does not politely retreat. It persists, adhering to glass and concrete.
With average temperatures rising 2.36°C above the historical average, the summer of 2025 was officially the hottest in Japan since records have been kept since 1898. A national record of 41.8°C was set by thermometers in Isesaki. Just that figure is shocking. The fact that this was the third year in a row that summer temperatures broke records is perhaps more concerning. Previously disregarded patterns now seem suspiciously consistent.
| Category | Details |
|---|---|
| Country | Japan |
| Key Authority | Japan Meteorological Agency (JMA) |
| Record Temperature | 41.8°C (Isesaki, Gunma Prefecture, August 2025) |
| Recent Trend | Hottest summers recorded consecutively from 2023–2025 |
| Ocean Factor | Warming Kuroshio Current and elevated Pacific sea surface temperatures |
| Health Impact | Over 100,000 heatstroke hospitalizations in 2025 |
| Expert Voice | Yoshihiro Iijima, Climatology Professor, Tokyo Metropolitan University |
| Research Contributor | Yoshihiro Tachibana, Mie University |
| Official Data Source | Japan Meteorological Agency – https://www.jma.go.jp/jma/indexe.html |
| Climate Analysis Reference | World Meteorological Organization – https://wmo.int/ |
Rising sea surface temperatures, enduring high-pressure systems, and a shifting subtropical jet stream have all been identified by scientists at the Japan Meteorological Agency as contributing factors. It’s possible that each of these could have contributed to a challenging summer on its own. When combined, they created something more akin to a climatic vice. According to reports, the sea temperatures around Japan are warming two to three times more quickly than the global average, adding humidity to already hot cities.
Last October, thermometers in Kagoshima continued to register 35°C. The autumn leaves, which usually turned red by the middle of the month, continued to be stubbornly green. The calendar doesn’t seem to be in sync with the mood anymore. Forecasts for cherry blossoms seem more and more hesitant, as though tradition is battling physics.
Japan’s four-season identity may be condensing into two dominant extremes: a longer summer and a shorter winter, according to researchers like Yoshihiro Tachibana at Mie University. The culturally valued transitions of spring and autumn, which are praised in poetry and food, seem to be dwindling. It’s difficult to ignore how ingrained seasonal rhythms are in Japanese society as you watch this play out, from fashion cycles to school semesters.
A smaller but significant role is played by the warming seas. The Kuroshio Current, sometimes referred to as Japan’s Gulf Stream, has been pushing warmer waters northward while meandering in peculiar ways. Surface temperatures have increased significantly above historical averages off the coast of Tōhoku and even toward Hokkaido. More moisture in the atmosphere due to warmer oceans causes heavy rains, such as the ones that ravaged the Noto Peninsula in 2024. What used to be considered a “100-year rainfall event” now appears to happen far too frequently.
But the most immediate danger is heat. In 2025, more than 100,000 people were admitted to hospitals for heatstroke, many of whom were elderly residents who were reluctant to use air conditioning because electricity prices were rising. A silent response to a climate that no longer feels forgiving is the reported practice of volunteers visiting elderly residents in certain Tokyo neighborhoods during the hottest hours of the day.
Agriculture is struggling. Vegetable yields are erratic, rice crops suffer from extended heat stress, and fisheries are reporting changes in species distribution as marine life moves northward in pursuit of cooler waters. Whether adaptation measures can keep up with the rate of temperature increase is still up in the air. Some farmers are investing in irrigation systems, changing planting dates, and experimenting with heat-resistant rice varieties. However, adaptation has its bounds.
Typhoons are also changing. Storms can intensify quickly prior to landfall due to persistently high ocean temperatures. A preview of this pattern was provided by Typhoons Nakri and Halong in 2025, which brought swiftly followed by torrential rains and destructive winds. The storms lasted longer than anticipated, which raises the possibility that warming seas are causing changes in atmospheric steering patterns.
Urbanization makes the problem worse. In densely populated areas of Tokyo, the heat island effect can trap heat between asphalt roads and glass towers, increasing temperatures by up to 3°C. It feels almost magnified to walk through Ginza on a late summer afternoon as sunlight bounces off high-rise windows. Perhaps what nature has already intensified is being amplified by cities themselves.
A change in psychology is also taking place. Once relatively quiet in comparison to discussions in Europe, climate change is now a more common topic of conversation in Japan. Parents talk about how the intense heat forced the cancellation of school sports days. Restaurant owners are concerned about the erratic supply of seafood. Climate-resilient infrastructure and renewable energy appear to be on the verge of becoming necessities, according to investors.
International climate assessments show that Asia is warming at a rate that is almost twice as fast as the global average. Instead of being an anomaly, Japan’s experience might serve as an early warning. The processes involved—warmer currents, slowing westerlies, and Arctic amplification—are not unique occurrences. They are linked parts of a larger change in the planet.
It seems like something fundamental is slanting. Gradually, not suddenly. Typhoons, earthquakes, and volcanic activity are all natural occurrences that Japan has long been used to. Climate change, however, is distinct. Expectations are being subtly reshaped, compounded, and incrementally altered.
