Kumagaya is forecast to experience its first extreme-heat day on July 21 with temperatures reaching 40°C [1], [2].
This surge in temperature signals a dangerous peak in the summer season, placing millions of residents at risk of heat-related illness as high temperatures spread across the country.
Forecasters predict a maximum temperature of 39°C in Nagoya [3], [4] and 36°C in Tokyo [5], [6]. The intensity of the heat has prompted heat-stroke alerts in 42 prefectures, covering 43 regions [7], [8].
Meteorologists said the spike is due to a strong Pacific high-pressure system. This system is maintaining clear skies and causing intense daytime heating across the archipelago [9], [10].
While the morning and early afternoon will remain clear, the extreme temperature rise is destabilizing the atmosphere. This volatility creates a risk of sudden weather changes later in the afternoon [1], [2].
Local authorities said residents should take precautions against the heat. The current weather pattern suggests a possibility of consecutive extreme-heat days throughout the week [1].
“Kumagaya is forecast to experience its first extreme-heat day on July 21 with temperatures reaching 40°C”
The arrival of a 'kokushobi' (extreme-heat day) in Kumagaya—a city known for some of Japan's highest temperatures—highlights the increasing volatility of the region's summer climate. The combination of extreme heat and atmospheric instability often leads to sudden, severe thunderstorms, complicating public health efforts to manage heat-stroke risks while simultaneously preparing for flash weather events.
