Japan has endured its hottest summer on record in 2025, with the nationwide average temperature soaring 2.36 degrees Celsius above the long-term norm, according to the Japan Meteorological Agency (JMA).
This unprecedented figure marks the highest since recordkeeping began in 1898, surpassing the previous highs set in 2022 and 2023, which were 1.76 degrees Celsius above average. Experts warn the latest figures point toward an escalating climate crisis that is making extreme weather the new norm.
The scorching temperatures gripped the country from early June and persisted relentlessly through August. On August 5, Isesaki in Gunma Prefecture registered a staggering 41.8 degrees Celsius, setting a new all-time national high. By the end of the month, Japan had experienced nine days of temperatures exceeding 40 degrees Celsius, breaking all previous records.
The JMA characterized this season as one of “abnormal heat,” underscoring the dangers posed to public health, agriculture, and infrastructure. Heat-related illnesses surged, while power grids faced increased pressure due to soaring demand for air conditioning.
Environmental experts in Japan have called for urgent adaptation measures, such as expanding green urban spaces and investing in climate-resilient infrastructure. They also stress the importance of global cooperation to curb greenhouse gas emissions and slow the pace of warming.
As the nation reflects on this record-breaking summer, concerns are mounting about whether 2026 could bring even more extreme temperatures.