The Japan Meteorological Agency forecast a maximum temperature of 40°C [1] for Kumagaya City in Saitama Prefecture on Tuesday.
This extreme weather marks the first "kokusho-bi," or extremely hot day, of the year for the region. The intensity of the heatwave has forced the government to issue heat-stroke alerts for 42 prefectures [2], the highest number of alerts recorded in a single day this year.
Officials said the conditions are "disaster-level" heat [3]. The alerts span a vast geographic area, stretching from Okinawa in the south to the Tohoku region in the north [2]. The widespread nature of the warning highlights the scale of the current heatwave and the potential risk to public health across the archipelago.
Local residents in affected areas reported immediate physical distress due to the rising temperatures. One woman on the scene said the sweat was unbearable and that she felt dizzy [4]. She also said that the extreme difference between indoor and outdoor temperatures was difficult to endure [4].
While the Japan Meteorological Agency focused on Kumagaya, other reports indicated similar extremes elsewhere. Some forecasts placed the highest temperatures in Toyoda, Aichi, at 41°C, and in Nagoya and Gifu at 40°C [2]. These figures underscore a broader pattern of extreme heat affecting multiple regions of Japan simultaneously.
Public health officials continue to urge citizens to stay hydrated and use air conditioning to avoid heat-related illnesses. The record-breaking number of prefectures under alert suggests that the heat is not isolated to a few urban heat islands, but is a systemic weather event affecting nearly the entire country.
“The Japan Meteorological Agency forecast a maximum temperature of 40°C for Kumagaya City.”
The issuance of heat-stroke alerts across 42 prefectures represents a significant escalation in the scale of Japan's summer heatwaves. By designating 40°C as a "kokusho-bi" (extremely hot day) and labeling the weather as "disaster-level," authorities are signaling that the heat has moved beyond a seasonal inconvenience to a critical public health emergency requiring national coordination.
