The Japan Meteorological Agency has created a new term for extreme heat. Kokusho-bi literally means brutally hot day in Japanese. This new term refers specifically to any day with a high temperature of at least 40 degrees Celsius. Consequently residents and weather forecasters now have a precise label for severe heat events. Kokusho-bi recently appeared next to the 40 C mark on a thermometer in Kumagaya, Saitama Prefecture.
Kumagaya is famous as one of Japan’s hottest cities. A large thermometer stands there during summer months. The city updates this thermometer daily at 11 a.m. and 2 p.m. It shows the local temperature from the Kumagaya Meteorological Office. Therefore residents can see immediately if a day qualifies as a kokusho-bi. The agency introduced this term to raise public awareness about dangerous heat levels.
Japan has experienced rising summer temperatures over the past decade. Heatwaves now occur more frequently across the Japanese archipelago. In 2023, several cities recorded temperatures above 40 C for multiple consecutive days. Elderly populations face particular risks during such extreme heat events. The government has urged people to stay indoors and use air conditioning. Nevertheless some households still limit electricity usage due to cost concerns.
. Global warming continues to push summer temperatures higher each year. Urban heat island effects worsen conditions in cities like Kumagaya and Tokyo. The meteorological agency hopes that a specific term will improve public response. When people hear kokusho-bi on weather forecasts, they should take immediate precautions. These precautions include drinking water frequently and avoiding outdoor activities.
The new term joins other Japanese weather vocabulary like guerilla rainstorm. Guerilla rainstorm describes sudden, localized heavy downpours. Similarly, kokusho-bi fills a gap in describing extreme heat thresholds. Local governments may use kokusho-bi to trigger heat emergency protocols. Schools and businesses could adjust schedules accordingly. The thermometer in Kumagaya will continue displaying this term prominently. Tourists and locals alike now recognize the danger of a kokusho-bi. Japan’s aging population requires clear communication about heat risks. Therefore this new term represents a practical step toward saving lives. The agency will monitor how effectively kokusho-bi changes public behavior. Early signs suggest that people take the term seriously when they see it.
