Japan faces the hottest summer in 127 years and records 41.8 °C in Isesaki

COP30 – Will meat become more expensive with global warming? The Japanese summer of 2025, between June and August, became the hottest ever recorded since the beginning of the historical series, in 1898, with average temperatures 2.36°C above the standard. Thermometers set records at 123 meteorological stations across the country, with the city of Isesaki recording a new national high of 41.8°C on August 5. According to the Japan Meteorological Agency (JMA), there were 30 occurrences of temperatures above 40 °C in the period, easily surpassing the previous annual record of 17 episodes, which occurred in the summer of 2018. The extreme heat seen in Japan makes up a persistent scenario of weather events faced by the country throughout 2025. Even with the arrival of autumn in the archipelago, the heat has not completely disappeared. Last Sunday, thermometers registered 35 °C in the southern city of Kagoshima, unusual for the time. More than 30 locations recorded records for the month of October. Over the past four decades, Japanese summers have gotten three weeks longer Louise Delmotte/AP Photo/picture alliance “Perfect storm” puts pressure on temperatures “The most basic reason for the increase in heat is global warming,” said Yoshihiro Iijima, a professor of climatology at Tokyo Metropolitan University. “This year we saw very warm surfaces in both the Pacific Ocean and the Sea of ​​Japan, that is, on both sides of the Japanese islands, which contributed to above-average humidity and warmer air over land,” he told DW. A high-pressure system intensified the warming of ocean waters for an extended period this summer, Iijima explained, while a subtropical jet stream moved significantly toward the North Pole. “These conditions combined are something of a ‘perfect storm’ that has contributed to the records recorded so far this year,” Iijima said. “We’ve broken records for three years in a row, and that’s an extremely worrying trend. I would already be worried about a gradual increase in heat, but we’re seeing unusual increases.” Global warming as a key factor In light of the extreme conditions, the JMA convened an Advisory Panel on Extreme Climate Events to discuss the issue. “The records observed in Japan in the summer of 2025 would virtually never have occurred under the assumption of no effects of global warming,” they said in a study published in late September. “Unprecedented summer averages were observed for three consecutive years (2023 to 2025), far exceeding the linear trend projected based on the period 1995 to 2024.” Hotter summers harm crops More than 100,000 people were hospitalized for heatstroke in Japan this summer Yuichi Yamazaki/AFP The constant heat could have extreme consequences for the country, points out Iijima. “The impact on the Japanese agricultural sector will be serious. Rice production is expected to fall because the crop cannot withstand the heat and lacks adequate water,” he said. Experts have also observed reductions in catches in the fishing sector, as traditional species migrate north in search of cooler waters. The heat also has a more direct impact on the Japanese population. More than 100,000 people were hospitalized between May 1 and early October for heatstroke treatment. This represents a 4% increase on last year, which was already a record, with the elderly particularly affected by the combination of high temperatures and high humidity. Iijima also warns that extreme heat tends to generate more powerful typhoons. Typhoon Nakri passed through the Izu archipelago, south of Tokyo, last Monday, a week after Typhoon Halong hit the same region. The first storm caused one death, in addition to damaging buildings on the islands and causing landslides. Winds reached 180 km/h, bringing unusual amounts of rain. “Persistent high water temperatures near Japan allow these typhoons to last longer and become more powerful and destructive,” explained the professor. “And as conditions get even hotter, that will make them even more dangerous.” “Nation of two seasons” Research conducted by a team led by Yoshihiro Tachibana, professor in the Department of Environmental Science and Technology at Mie University, determined that Japanese summers became three weeks longer between 1982 and 2023 as a result of climate change. “This happens because of global warming and the constant increase in sea temperatures around Japan,” said Tachibana, highlighting that these readings are rising two or three times faster than in other parts of the planet. “This is due to the summer heat, which is even greater here than elsewhere in the world because of warmer westerly winds and the impact of the warm Kuroshio current, which brings water from the tropical Pacific to Japan,” he said. Although Japanese summers are now longer, winters tend to remain similar in length due to the country’s exposure to Arctic winds, Tachibana explained. Fall and spring, however, are shrinking. “Japanese summers are expected to continue to get longer because of global warming, which means spring and autumn will get even shorter,” he said. “In just 30 years, these seasons could disappear unless something is done to curb the effects of global warming. Otherwise, in 30 years Japan will become a nation of just two seasons.” Author: Julian Ryall

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