The Japan Meteorological Agency warns of continued atmospheric instability on June 28, 2026, bringing rain and potential thunderstorms to eastern regions [1].
These weather patterns pose risks of sudden flash flooding and heat-related illnesses across the archipelago. The combination of extreme heat in the west and volatile storm cells in the east complicates regional travel and public safety efforts.
Forecasters report that a low-pressure area is forming between two high-pressure systems [1]. This configuration allows moist air to flow over the region, creating the instability that leads to sudden weather shifts [1].
In the Kanto and Tokai regions, rain is expected in the morning but may temporarily stop [2]. TBS NEWS DIG said rain is expected to return after the evening, with some areas experiencing stronger rainfall and thunderstorms [2].
Western Japan, including the Kansai, Chugoku, Shikoku, and Kyushu regions, will remain under the influence of high pressure [1]. While this ensures sunny skies, it will maintain oppressive heat. Predicted maximum temperatures for June 28 include 37 degrees Celsius in Okayama and Hiroshima, 36 degrees Celsius in Osaka, Fukuoka, and Kagoshima, and 35 degrees Celsius in Nagoya [1].
This heat follows a period of record-breaking temperatures. In Hita, Oita Prefecture, temperatures exceeded 40 degrees Celsius, marking the first time such heat has been recorded in Kyushu [1].
Other regional forecasts for June 28 include 32 degrees Celsius in Kanazawa and Matsue, 31 degrees Celsius in Nagano, and 30 degrees Celsius in Tokyo and Niigata [1]. Northern areas will be cooler, with Sapporo predicted at 26 degrees Celsius and Kushiro at 23 degrees Celsius [1].
Despite the sunny forecast for western Japan, officials said the weather may change suddenly [1].
“Rain is expected to return after the evening, with some areas experiencing stronger rainfall and thunderstorms.”
The simultaneous occurrence of extreme heat in western Japan and atmospheric instability in the east highlights the volatile nature of the region's early summer transition. The record-breaking 40-degree temperature in Kyushu indicates a trend toward more severe heatwaves, which, when coupled with sudden thunderstorms, increases the risk of infrastructure strain and public health emergencies.
