The Japan Meteorological Agency has introduced the term "kokushobi" to describe days when the maximum temperature exceeds 40 °C [1].
The creation of this linguistic marker reflects the growing frequency of extreme heat across the archipelago. As climate change alters regional weather patterns, the agency seeks to provide a specific designation for temperatures that pose significant risks to public health.
Literally translated as "cruelly hot day," kokushobi serves as a warning for the most severe heat events [1]. The term distinguishes these peaks from standard heatwave warnings, signaling a level of intensity that requires urgent caution. This addition to the Japanese lexicon acknowledges that previous temperature categories no longer sufficiently capture the reality of modern summers.
Officials said the term is intended to underscore the impact of climate change on Japanese society [2]. By naming the phenomenon, the government aims to increase public awareness and encourage preventative measures during these dangerous spikes. The move comes as Japan experiences more frequent and intense heatwaves that strain urban infrastructure and healthcare systems.
While the agency has long monitored temperature trends, the formal adoption of a word meaning "cruel" highlights the perceived severity of current conditions [1]. The threshold of 40 °C [1] represents a critical point where heat exhaustion and heatstroke risks accelerate rapidly for the general population.
This linguistic shift is part of a broader effort to adapt to a warming planet. The agency said the goal is to provide a clear marker for the public to recognize when heat has reached a lethal or "cruel" level [2].
“The term "kokushobi" literally translates to "cruelly hot day."”
The introduction of 'kokushobi' indicates that extreme heat is no longer viewed as a statistical anomaly in Japan, but as a recurring seasonal reality. By shifting from purely numerical warnings to a term evoking emotional and physical distress, the government is attempting to trigger a stronger psychological response from the public to reduce heat-related fatalities.
