Record-breaking heatwave in August 2025: Japan sees highest temperature of 41.8°C ever recorded
Record-Breaking Heatwave Grips Japan in Summer 2025
Japan has been experiencing an unusually hot summer in 2025, with multiple cities recording temperatures above 40°C due to an intense heatwave driven by human-caused climate change.
The heatwave has been particularly severe in northern Japan, where cities like Kitami in Hokkaido recorded a high of 39°C on July 24, 2025 – a temperature rarely seen in this region. This summer has been the hottest on record, with July 2025 being the warmest since records began in 1898, and June also setting new temperature highs.
Cities across the country have been experiencing temperatures far above their averages. For instance, on August 11, 2020, Kiryū in Gunma reached 40.5°, while Hamamatsu in Shizuoka reached 40.9° on August 16, 2020. On August 10, 2013, Kōfu in Yamanashi reached 40.7°, and Nagaoka in Niigata reached 40.6° on August 15, 2019.
The heatwave intensified partly because of an early end to the rainy season and low rainfall, causing drought conditions that further exacerbated the heat. Climate scientists attribute these extreme temperatures to the impact of continuous fossil fuel emissions leading to global warming, making such heatwaves at least five times more likely than in a pre-industrial climate.
The highest temperature ever recorded in Japan was broken on August 5, 2025, when Isesaki in Gunma reached 41.8°. This record-breaking temperature was also matched in Shizuoka on the same day. Other cities that experienced all-time highs include Hatoyama in Saitama (41.4°), Koga in Ibaraki (40.6°), and Kumagaya in Saitama (40.7°).
It's worth noting that Japan's top temperature remained unchanged for more than 70 years until August 16, 2007, when it hit a new high of 40.9° in both Tajimi, Gifu, and Kumagaya. This record was tied again in 2018, when Tajimi reached 40.8° on July 18, and Mino in Gifu reached 40.6° on the same day.
The extreme heat has posed significant health risks and threatened water supplies and agriculture. Climate change experts warn that such events will become more frequent and severe in the future unless urgent action is taken to reduce greenhouse gas emissions.
References:
[1] Japan Meteorological Agency. (2025). Record-breaking heatwave in summer 2025. Retrieved from https://www.jma.go.jp/en/events/heatwave/2025/
[2] National Institute for Environmental Studies. (2025). Climate change and extreme heat in Japan. Retrieved from https://www.nies.go.jp/en/research/global_change/extreme_heat/
[3] Ministry of the Environment. (2025). Impact of climate change on extreme heat events in Japan. Retrieved from https://www.env.go.jp/en/climate/impact/heat/
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