Japan coins new word for days above 40 C as extreme heat becomes the norm

As extreme heat becomes a fixture of daily life in Japan, the country has coined a new word for it. The New York Times reported Thursday (local time) that Japanese authorities have officially adopted the term "kokushobi" — meaning "day of brutal heat" — to designate any day when temperatures exceed 40 degrees Celsius.

Japan's health and meteorological authorities had long struggled to convey the dangers of extreme heat effectively. Last year saw a record number of heatstroke patients, and all-time high temperatures were recorded across the country, yet officials concluded that standard heat warnings alone were not enough to raise public awareness.

In response, the Japan Meteorological Administration held a public vote earlier this year to choose an official name for days when temperatures reach 40 C or above, aiming to communicate the severity of extreme heat intuitively and prompt immediate action from the public.

The term "kokushobi" won more than 40 percent of the vote and was ultimately selected as the official designation.

The term was first used on July 22, when three cities in central Japan recorded temperatures of 40 C for the first time this year. Authorities urged residents to stay indoors, use air conditioning and drink plenty of water.

The warning appeared to have an effect. Visitor numbers dropped noticeably at major tourist sites, including Osaka Castle and Kiyomizudera temple in Kyoto.

Kawasato Taro, deputy director of the climate prediction division at the Japan Meteorological Administration, said people process numbers differently, making it hard to convey danger through temperature figures alone. "Just hearing the name 'day of brutal heat' lets people intuitively understand that today is a dangerous day," he said.

More than 400,000 people took part in the public vote, which the meteorological administration conducted between February and March. Around 10 candidate terms were put forward — including "day of dangerous heat," "day of drenching sweat" and "sauna day" — with the final list drawn up in consultation with media and linguistics experts before "kokushobi" was chosen.

The heat threat shows no sign of easing. According to the National Fire Agency, 14 people died from heat-related illness last week, even before the first "kokushobi" was declared.

The phenomenon is not unique to Japan. Britain's Met Office has issued "extreme heat warnings" since 2021 to highlight the impact of heat on health, infrastructure and public services. During the heat wave that struck Europe last month, the agency issued its highest-level red alert.

The UK Health Security Agency also operates a "heat health alert" system to notify medical institutions of risks to the elderly and other vulnerable groups.

Taiwanese media described this summer's weather as feeling "like a sauna" and being "roasted like a sweet potato," while health authorities in Shenzhen, in southern China, used the phrase "barbecue mode" to describe the heat earlier this month. During that period, 62 people in Shenzhen were transported by ambulance with heatstroke, two of whom died.

According to the Japan Meteorological Administration, temperatures of 40 C or above were recorded in 30 locations nationwide last year. The highest reading was 41.8 C, set in Isesaki, Gunma Prefecture, north of Tokyo.

Heatstroke is a heat-related illness in which the body's temperature-regulation system fails, placing strain on the heart. Symptoms can range from confusion, dizziness and nausea to elevated heart rate and difficulty breathing.

Last year, more than 100,000 people in Japan were rushed to emergency rooms with heatstroke between May and September — the highest figure since the country began tracking such data in 2008.