Dangerous heat continues across western Japan with temperatures forecast to reach 38°C in Ōita [1].

The extreme weather poses significant public health risks, prompting officials to issue heat-alert warnings across multiple regions as a strong Pacific high-pressure system settles over the country.

The Japan Meteorological Agency (JMA) said that heat-alert warnings have been issued for 14 prefectures [4]. This intense heat has already caused the rainy season to officially end in southern Kyushu [5].

In western Japan, forecasts for today show high temperatures of 34°C in both Osaka and Hiroshima [6, 7]. In the east, Tokyo's temperature for today is forecast to be between 31°C [2] and 35°C [2].

Meteorologists said the heat is expected to expand to eastern Japan tomorrow. Forecasts indicate that Tokyo could see temperatures rise to 38°C [3]. Some reports suggest that maximum temperatures over the coming weekend in the Kanto and Chubu regions could approach 40°C [2].

The current weather pattern is driven by a strong Pacific high-pressure system [8]. This system is pushing heat across the archipelago and displacing the seasonal rains that typically characterize this time of year in the south.

“Dangerous heat continues across western Japan with temperatures forecast to reach 38°C in Ōita.”

The rapid transition from the rainy season to extreme heat, combined with a strong Pacific high-pressure system, increases the risk of heatstroke and puts pressure on energy grids for cooling. The expansion of this heatwave into the densely populated Kanto region and Tokyo suggests a widespread public health challenge for the remainder of the week.