In April 2026, the Japan Meteorological Agency (JMA) introduced a new word – "kokushobi" – to describe days when temperatures exceed 40°C. The term has been translated as "cruelly hot", "brutally hot" or "severely hot" by media.

This is the first new heat-related weather term created in Japan since 2007, when "moshobi" was introduced to describe days exceeding 35°C. Although kokushobi has been used since 2022 by weather forecasting company, the Japan Weather Association, the JMA formally adopted it this year to more effectively encourage vigilance against extreme heat in the face of the growing severity of climate risks linked to global warming.

The three hottest years ever recorded globally happened between 2023 and 2025, according to the European Union's weather agency, the Copernicus Climate Change Service. This was the first time the recorded global average temperature over a three-year period exceeded 1.5°C above pre-industrial levels, raising concerns about the escalating impacts of climate change.

Supporting air conditioner use

Japan’s summers are characterized by high temperatures and intense humidity. This makes it difficult for sweat to evaporate, significantly raising the risk of heatstroke. In this environment, air conditioner use goes beyond comfort – it protects lives.

And so, it was good news that, in May 2026, Japan’s Ministry of Economy, Trade and Industry announced that it had secured sufficient electricity supply for peak summer demand. It waived a nationwide power conservation request for the third consecutive year.

Despite concerns over fuel procurement linked to geopolitical instability, the ministry stated that Japan’s dependence on oil-fired power generation remains relatively limited and that liquefied natural gas (LNG) and other energy sources would help meet summer demand this year. The government is also promoting energy-efficient appliances to encourage more efficient electricity use.

In Tokyo, the metropolitan government announced a four-month waiver of water charges for around 8 million households. The measure is expected to reduce monthly household expenses by approximately JPY 5,000. Since many heatstroke cases occur indoors, the policy aims to ease utility cost burdens and encourage residents to use air conditioning without hesitation despite rising living costs.

Promoting heat acclimatization

The human body cannot immediately adjust to sudden heat, and insufficient adaptation significantly increases the risk of heatstroke.

That's why the Japanese government is also promoting “heat acclimatization”. This is the process of gradually adapting the body to hot weather before the peak of summer arrives.

Initiatives encouraging light exercise, warm baths and other activities that improve the body’s ability to sweat efficiently are gaining attention, as a result. Local governments, companies and media organizations are now actively sharing information about heat acclimatization methods and their importance. This is helping to raise public awareness of building heat resilience before summer peaks.

A new market for heatstroke prevention

Heatstroke prevention measures were made mandatory in Japanese workplaces from June 2025. As a result, workplace deaths caused by heatstroke fell by half in 2025 compared with the previous year.

At the same time, the market for heatstroke prevention services is rapidly expanding. For example, Japanese food and beverage company Suntory’s corporate heatstroke prevention service combines electrolyte-enhanced hydration drinks, improved access to beverages through vending machines and employee education and safety seminars to support workers in high-temperature environments.

And Daikin, an air conditioning and heating manufacturer, has partnered with Future Design Shibuya and Osaka University to launch the Shibuya Green Shift Project. It is experimenting with cooling spots, energy-efficient building management and heatstroke risk maps, among other iniatiatives.

Such collaboration between the public sector, private companies and local communities is helping to build a heat-adaptive society.

Building resilience in an era of extreme heat

As climate change intensifies, protecting people from extreme heat has become essential to safeguarding lives and maintaining normal societal functions such as work and community-building.

Japan’s cross-sector response offers a model for how societies can adapt to increasingly dangerous heat while strengthening climate risk resilience.

As temperatures continue to rise globally, these efforts offer valuable lessons for other countries facing a hotter future.