Japan has experienced record-breaking weather events through 2025, with experts raising concerns about their potential impact.
The summer of 2025 was the hottest ever recorded in Japan, with nationwide average temperatures 2.36 degrees Celsius above average since records began in 1898. Isesaki city in Gunma Prefecture set a new national record of 41.8 Celsius (107.2 Fahrenheit) on August 5.
The Japan Meteorological Agency (JMA) said its network of more than 1,300 stations recorded temperatures 30 times when temperatures topped 40 degrees, far more than the 17 occasions set in summer 2018, the last annual record.
And even though autumn has arrived across the archipelago, summer hasn’t completely ended, with temperatures in the southern city of Kagoshima hitting 35 degrees this Sunday. Record highs were recorded in the month of October at more than 30 places across the country.
‘Abnormally high rise’ in temperatures
“The most fundamental cause of rising temperatures is global warming,” said Yoshihiro Iijima, a climate science professor at Tokyo Metropolitan University.
“This year we’ve seen very high surface temperatures in both the Pacific Ocean and the Sea of Japan, so on both sides of the islands of Japan, which has contributed to higher than average humidity and warmer air temperatures over land,” he told DW.
Iijima said ocean temperatures have increased due to a persistent high pressure system that lingered over Japan for a long time this summer, while the subtropical jet stream over Eurasia shifted significantly northward after June.
“These conditions combined to form a kind of ‘perfect storm’ have contributed to the record temperatures we have experienced so far this year,” Iijima said. “But we’ve broken records three years in a row and that’s an extremely worrying trend. I would have been worried about a gradual increase in temperatures, but we’re seeing unusually high increases.”
Global warming as a major factor
Conditions have been so dramatic this year that the JMA convened its advisory panel into extreme climate events, with researchers also pointing the finger at broader climate change.
“Record high temperatures observed around Japan in the summer of 2025 that would never have actually occurred with the assumption of no impacts from global warming are significant,” they said in a study published in late September.
“The rate of temperature increase due to global warming has accelerated in recent years,” the panel said. “Record high summer average surface air temperatures are observed in Japan for three consecutive years (2023 to 2025), far exceeding the projected linear trend of temperatures based on the period 1995 to 2024.”
Extreme heat damages crops, brings more destructive storms
Iijima says the rising heat could have serious consequences for the country.
“The impact on Japan’s agricultural sector will be severe, with rice production reduced because the crop cannot tolerate the heat and there is insufficient water,” he said. Experts have also noted changes in the country’s fishing sector, with catches declining and a greater share of traditionally caught species moving north in search of cooler waters.
But the heat also has a more direct impact on the Japanese population, with more than 100,000 people admitted to hospitals for treatment of heatstroke between May 1 and early October. This is 4% more than last year’s figure – another record high – with the elderly particularly affected by the combination of high temperatures and high humidity.
Iijima also warned that extreme heat could lead to more powerful storms.
Typhoon Nakari passed through the Izu island chain south of Tokyo on Monday, a week after Typhoon Halong struck the same area. The storm first caused one death, but also damaged buildings and caused landslides throughout the islands. The JMA said Typhoon Nakri produced winds of up to 180 kilometers per hour (112 mph) and dropped unusually large amounts of rainfall.
“The sustained high temperatures of surface waters near Japan enable these typhoons to last longer and become more powerful and destructive,” Iijima said. “And as conditions get even warmer, that will make them even more dangerous.”
No more spring and autumn?
The research, conducted by a team led by Professor Yoshihiro Tachibana of Mie University’s Department of Environmental Science and Technology, showed that Japanese summers are set to become three weeks longer between 1982 and 2023 as a result of climate change.
“This is due to global warming and the continued warming of sea surface temperatures around Japan,” Tachibana said. He reported that ocean temperatures around Japan are rising two or three times faster than elsewhere on the planet.
“This is due to the high summer temperatures, which are even higher here than in other parts of the world due to the influence of warm westerly winds and the warm Kuroshio Current, which brings water from the tropical Pacific to Japan,” he said.
Tachibana said summers in Japan have now become longer, but winters have also become shorter due to exposure to Arctic winds. However, autumn and spring are shrinking.
“I expect Japanese summers to become longer due to global warming, which means spring and autumn will become even shorter,” he said. “In as little as 30 years, they could effectively disappear unless something is done to curb the effects of global warming. But if not, in 30 years Japan will become a country with only two seasons.”
Edited by: Darko Janjevic