Japan's Ministry of the Environment and the Japan Meteorological Agency have issued heat-stroke alerts across seven prefectures in the Kyushu and Chugoku regions [1].

The alerts come as a strong Pacific high pressure system pushes temperatures higher across the archipelago, creating a critical risk for heat-related illnesses during an unusually intense heatwave.

In northern Kyushu, several areas have already recorded "extremely hot days." Yatsushiro in Kumamoto Prefecture and Hita in Oita Prefecture both recorded maximum temperatures of 35.5 degrees Celsius [1]. Karatsu in Saga Prefecture recorded a maximum of 35.1 degrees Celsius [1].

Forecasts indicate the heat will intensify further. Temperatures in Kurume, Fukuoka, and Hita, Oita, are expected to reach 38 degrees Celsius [1]. Meanwhile, Kumamoto and Saga prefectures are expected to see highs of 37 degrees Celsius [1].

The heat is not limited to the south. In the Kanto and eastern regions of Japan, Kumagaya in Saitama Prefecture is expected to reach 35 degrees Celsius [1]. Central Tokyo is forecast to reach 32 degrees Celsius [1].

Authorities issued the alerts for the seven affected prefectures to warn the public of the extreme risk associated with the current weather pattern [1]. The combination of high temperatures and the atmospheric pressure system has created conditions where heat-stroke risks are judged to be extremely high [1].

These weather patterns were reported and forecasted on May 25 [2].

“Seven prefectures in Kyushu and Chugoku regions are under alert”

The issuance of heat-stroke alerts as early as May indicates a shift toward more aggressive early-season temperature spikes in Japan. When a strong Pacific high pressure system dominates the archipelago this early, it puts significant strain on public health infrastructure and energy grids before the peak summer months of July and August.