TOKYO, April 17, 2026 (BSS/AFP) - Blistering temperatures rising to 40C and above will now be branded "cruelly hot" or "kokusho-bi" in Japan, the weather agency said Friday, as heatwave days become increasingly frequent in the region.

By using this designation, the Japan Meteorological Agency (JMA) "will more effectively call for vigilance against extremely high temperatures", it said.

Last year, Japan sweltered through its hottest summer since records began in 1989 -- with warmer days on the rise globally due to climate change.

To come up with the new category, JMA conducted a survey with the public and received responses from 478,000 people before adopting "cruelly hot", which was deemed the most popular.

Coming in second was "super-extremely hot day" or "cho-mosho-bi" while "sauna day", "stay-at-home day" and "boiling day" were also among the choices, JMA said.

The new category joins terms already used by JMA for temperatures rising to 25C and higher (summer day), 30C and higher (midsummer day), and 35C and higher (extremely hot day).