THE ASAHI SHIMBUN
September 1, 2025 at 18:28 JST
Pedestrians battle the heat in Tokyo’s Chuo Ward on Aug. 31. (Minori Oshita)
Japan just experienced its hottest summer on record.
The record high national average temperature from June to August was 2.36 degrees hotter than average, the Japan Meteorological Agency said Sept. 1, without providing the figure.
It was the third straight record for summer heat, but it also indicated that the rise in temperatures could be speeding up.
For the previous record hot summers in 2024 and 2023, the average temperatures were 1.76 degrees higher than normal.
According to the JMA, westerly winds shifted northward over Japan throughout the summer, causing warm air from the south to cover the archipelago.
Additionally, two high-pressure systems—the Tibetan High from central Asia and the Pacific High from the ocean—both strengthened, leading to clear skies and higher temperatures.
Several heat records were set in the summer across Japan.
Temperatures of 40 degrees or higher were recorded at 25 locations nationwide.
Among 914 observation sites across Japan, 207 baked under their highest temperatures ever recorded.
Japan’s previous highest temperature of 41.1 degrees, set in Hamamatsu, Shizuoka Prefecture, in 2020, and Kumagaya, Saitama Prefecture, in 2018, was surpassed this year.
On July 30, the mercury hit 41.2 degrees in Tamba, Hyogo Prefecture. But that record was short-lived.
On Aug. 5, Isesaki city in Gunma Prefecture had a daily high of 41.8 degrees.
Maebashi and Isesaki in Gunma Prefecture, Kumagaya and Hatoyama in Saitama Prefecture, and Kuwana in Mie Prefecture each had two summer days with temperatures above 40 degrees.
Hita, Oita Prefecture, experienced 55 days above 35 degrees, while Kyotanabe in Kyoto Prefecture and Kofu in Yamanashi Prefecture each had 53 such days.
In addition to meandering westerly winds, high sea surface temperatures contributed to exceptional heat in Hokkaido.
On July 24, temperatures reached 39.0 degrees in Kitami, 38.8 degrees in Obihiro, and 38.6 degrees in Saroma, all in Japan’s northernmost main island.
(This article was written by Shoko Rikimaru and Keitaro Fukuchi.)
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