Japan has forecast its first "extreme heat day" (kokushobi), with a maximum temperature of 40 degrees Celsius or higher, since weather observations began. With Kumagaya, Saitama Prefecture, expected to reach a high of 40 degrees, a heatstroke alert was issued.
According to the Japan Meteorological Agency (JMA) and the Ministry of the Environment on the 21st, heatstroke alerts were issued for 44 areas across 42 prefectures from Tohoku to Okinawa. The day's highs were forecast at 40 degrees in Kumagaya, 39 degrees in Nagoya, 38 degrees in Saitama and Maebashi, and 36 degrees in Tokyo and Osaka.
The JMA has categorized days by maximum temperature: 25 degrees or higher as a "summer day," 30 degrees or higher as a "midsummer day," and 35 degrees or higher as an "extreme heat day" (moshobi). In April this year, it introduced "kokushobi," meaning a maximum temperature of 40 degrees or higher, as a new forecasting term to respond to extreme heat driven by climate change.
The heat wave is spreading across all of Japan. The previous day, 252 of 914 weather observation points recorded highs above 35 degrees, and 674 recorded 30 degrees or higher. Tokyo also recorded its first extreme heat day of the summer.
Human casualties are also mounting. According to the Tokyo Fire Department, 142 people in Tokyo alone were taken to hospitals the previous day with suspected heatstroke symptoms, of whom six were classified as severe cases. The JMA forecast that temperatures higher than normal would continue through July to September due to the influence of the Pacific high-pressure system.
The heat wave is also affecting industrial sites. The Nihon Keizai Shimbun, analyzing data from the U.S. National Oceanic and Atmospheric Administration (NOAA), reported that "Tokyo's temperature and humidity in July and August have recently risen to levels similar to Bangkok, Thailand, and Singapore."
An international study led by the British medical journal The Lancet estimated that Japanese workers lost an average of 43 hours of working time per person due to the heat last year. Japan's total labor loss reached about 2.89 billion hours annually, more than double the average of the 2010s.
Japan's construction industry has begun adjusting working hours. Konoike Construction will implement consecutive days off at some sites from July to September and increase Saturday work after October, when temperatures are lower, to reduce the workload during midsummer while maintaining annual working hours.
The heat response market is also growing rapidly. Household goods maker Kao is developing a cooling towel that retains its cooling effect longer than existing products, and more than 500 companies have already adopted related products. Workwear maker Workman is also expanding related product development, launching functional clothing designed for high-temperature environments of 45 degrees.
The Japanese government has made it mandatory for employers to establish heatstroke response systems at workplaces, but workplace heatstroke casualties reached a record high for the second consecutive year. Experts noted that "there are limits to cooling products alone," adding that "work methods that reduce heat exposure itself, such as adjusting working hours and reallocating labor hours by season, are needed."
