A severe heatwave has prompted heat-stroke alerts for 41 prefectures across Japan as temperatures are forecast to exceed 40°C [1].
This weather event poses a significant public health risk, as the extreme heat is described as disaster-level and is already causing emergency hospitalizations in urban centers.
Forecasters expect the peak of the heat to last until Friday, July 24 [1]. A strong high-pressure system, known as a "double high," is driving the surge in temperatures [1, 2]. In Nagoya and Kumagaya, maximum temperatures are expected to reach 40°C [1]. Specifically, Nagoya is forecast to experience temperatures of 40°C for two consecutive days [1].
Early morning readings on Wednesday showed the heat intensifying quickly. Central Tokyo reached 35.0°C by 9:30 [1]. In the Tokai and Kanto regions, other early observations included 37.5°C in Nagoya City and 37.3°C in Hatoyama, Saitama [1].
The Tokyo Fire Department reported that 10 people were transported by ambulance with suspected heat-stroke symptoms by 9:00 [1, 2].
Local residents have noted the unusual intensity of this season. "I have lived and grown up in Nagoya and am used to the heat, but this year is hot," said an 80-year-old woman in Nagoya [2].
Officials are monitoring the number of locations reaching "extreme heat day" status. Currently, 14 locations are approaching record levels [1]. While some reports suggest a smaller number of alerts, the primary forecast maintains that 41 prefectures remain under the heat-stroke warning [1].
“Temperatures are forecast to hit 40°C in Nagoya and Kumagaya.”
The occurrence of 'disaster-level' heat and the rapid onset of emergency transports in the early morning suggest that urban heat island effects are compounding the regional high-pressure system. With temperatures hitting 40°C in multiple cities, the strain on emergency services and the risk to elderly populations, who may have a higher tolerance for typical heat but are vulnerable to extremes, increase significantly.
