Western Japan will be mostly sunny with very high temperatures on Sept. 1, while northern regions face heavy afternoon rain [1].
These contrasting weather patterns create simultaneous risks of heat-related illness in the south and flooding in the north, with a wider threat of heavy rain nationwide expected later this week.
A high-pressure ridge over western Japan is driving the current heatwave [1]. Meteorologists from TBS NEWS DIG said a maximum temperature of 38°C is forecast in Toyooka, Hyōgo [1]. Other western cities are expected to see similar extremes, including 37°C in both Okayama and Matsue [1].
Fukuoka is forecast to reach 36°C [1], while Osaka and Kochi are expected to hit 35°C [1]. Kagoshima will be slightly cooler with a high of 34°C [1].
In contrast, northern Japan is bracing for wet conditions. A low-pressure system moving along a stationary front is bringing moist easterly flow toward Hokkaido and the northern Tōhoku region [1, 2]. Heavy rain is expected to begin in the afternoon [1, 2].
Temperatures in the north will remain significantly lower than in the west. Sapporo is forecast to reach a maximum of 24°C [1], and Aomori is expected to hit 26°C [1]. Niigata will see a high of 34°C [1].
The volatility is expected to increase toward the end of the week. A combination of a frontal system and an approaching typhoon may bring widespread heavy rain across the country [1, 2].
“Western Japan will be mostly sunny with very high temperatures on Sept. 1”
The simultaneous occurrence of extreme heat and heavy rain highlights the volatility of Japan's transition into September. The looming threat of a typhoon combined with a stationary front suggests a high risk of infrastructure stress and potential flooding across multiple prefectures by the end of the week.
