Climate change is having consequences on language — the creation of new words. Japan's Meteorological Agency (JMA) has introduced a new word into the Japanese dictionary. The word is "kokushobi," which literally means "cruelly hot day" or "harshly hot day". It will be used when describing or forecasting days when temperatures are 40ºC or above. There was an online poll of weather-based terminology. The questionnaire was because of the recent scorching weather. Website visitors selected their preferred word. There were 478,000 responses. The word kokushobi got nearly 203,000 votes.

There has been record-breaking heat in Japan. There have been days of 40ºC or above every year since 2018. In August 2025, a town in Gunma Prefecture recorded the highest temperature ever in Japan. The mercury rose to 41.8ºC. There were nine more days of 40ºC temperatures. More records were broken in 2025. This was the hottest year since records began in 1898. The Mainichi newspaper wrote: "Tokyo recorded 25 days over 35ºC, compared with an annual average of just 4.5 days. Kyoto logged 52 days above that, compared with an average of 18.5 days."