Full Breakdown
Japan Introduces "Kokushobi" to Address Rising Extreme Heat
4/18/2026, 12:54:17 AM
New Terminology for Extreme Heat Days
On April 17, 2023, the Japan Meteorological Agency (JMA) announced the addition of a new term, "kokushobi," meaning "severely hot day," to its weather-forecast lexicon. This decision reflects the increasing frequency of days with temperatures exceeding 40 degrees Celsius (104 degrees Fahrenheit) in Japan. The term was selected following an online survey conducted in February and March, which presented 13 candidates to the public alongside expert opinions. The JMA's classification system now includes other terms such as "natsubi" for summer days above 25 degrees Celsius, "manatsubi" for midsummer days above 30 degrees Celsius, and "moshobi" for extremely hot days above 35 degrees Celsius.
Context of Rising Temperatures
The introduction of "kokushobi" comes amid alarming climate trends in Japan. Since record-keeping began in 1872, there have been 108 days where temperatures exceeded 40 degrees Celsius, with 41 of these days occurring between 2023 and 2025. This statistic indicates that over one-third of such extreme heat days in the past 150 years have happened in just the last three years. The summer of 2025 was particularly notable, being the hottest on record, with average temperatures from June to August exceeding the 30-year average by 2.36 degrees Celsius.
Implications of Climate Change
Japan's warming trend is outpacing the global average, with temperatures rising by 1.13 degrees Celsius over the past century compared to the global increase of approximately 0.73 degrees Celsius. Scientists attribute this accelerated warming to the climate crisis, particularly the rising temperatures of surrounding waters, which exacerbate heat retention and lead to more intense weather phenomena, including heavier rainfall and stronger typhoons.
The health impacts of these extreme temperatures are significant, with heat-related hospitalizations surging during heatwaves. For instance, during the July 2018 heatwave, temperatures reached a then-record 41.1 degrees Celsius in Kumagaya, Saitama, resulting in 96 suspected heatstroke deaths among Tokyo residents over a single month.
Criticism and Concerns
Experts warn that if the current climate trends continue, Japan may face a future with only two distinct seasons, as spring and autumn become increasingly marginalized. This shift would mirror patterns observed across other parts of Asia, raising concerns about the long-term impacts on Japan's climate and cultural identity.
Official Statements
The JMA's decision to introduce "kokushobi" is seen as a necessary adaptation to the realities of climate change. The agency emphasized the importance of public awareness regarding extreme heat days and their potential health risks.
What's Next
Looking ahead, experts predict that record-breaking summers will continue, with forecasts indicating another extreme heat season in 2026. The ongoing climate crisis necessitates urgent action to mitigate its impacts on public health and the environment in Japan.
