Japan endures hottest June on record
Japan recorded its hottest June since records began in 1898, with average temperatures 2.34°C (4.21°F) above normal and over 200 locations registering highs of 35°C (95°F) or more, the Japan Meteorological Agency reported on June 30, 2025.
Image credit: Tsuyoshi Kozu
Japan recorded its highest-ever June temperatures in 2025, with the national monthly average exceeding the long-term normal by 2.34°C (4.21°F), the Japan Meteorological Agency (JMA) reported on June 30. Ocean surface temperatures along Japan’s Pacific coast also reached 1.2°C (2.2°F) above normal, matching the record set in June 2024.
A heatwave spanning June 16 to 18 was particularly severe, affecting most of the archipelago during what is usually the rainy season.
More than 200 weather stations recorded daily highs of 35°C (95°F) or more in June, the highest number ever for the month.
In Tokyo, 38.6°C (101.5°F) was observed in Nerima Ward, while Kumagaya City in Saitama Prefecture registered 39.1°C (102.4°F). For comparison, the previous highest national monthly temperature anomaly was +1.9°C (3.4°F), set in August 2010.
From May to September 2024, the Fire and Disaster Management Agency reported 97 578 heatstroke-related emergency transports, with 120 deaths occurring before hospital admission. Tokyo reported that more than 50% of cases involved people aged 65 or older, and 38% of incidents occurred indoors, mostly in homes without active air conditioning.
In response to the escalating toll, Japan implemented new workplace safety regulations effective June 1. Employers are now legally required to monitor environmental conditions and worker symptoms when temperatures exceed 31°C (88°F) or WBGT (Wet Bulb Globe Temperature) exceeds 28°C (82°F) for more than one hour. Noncompliance carries penalties of up to six months’ imprisonment or fines up to JPY 500 000 (USD 3 110). In 2024, a record 1 257 cases of heatstroke-related injury or death were recorded in workplaces.
Adaptation efforts have also included public cooling centers, air conditioner subsidies, and updated school policies. Energy grid operators are maintaining reserve margins above 7% to ensure stability during peak summer demand.
Reet is a science journalist and researcher with a keen focus on extreme weather, space phenomena, and climate-related issues. With a strong foundation in astronomy and a history of environmental activism, she approaches every story with a sharp scientific lens and a deep sense of purpose. Driven by a lifelong love for writing, and a curiosity about the universe, Reet brings urgency and insight to some of the most important scientific developments of our time.
Commenting rules and guidelines
We value the thoughts and opinions of our readers and welcome healthy discussions on our website. In order to maintain a respectful and positive community, we ask that all commenters follow these rules.