# Weather instability and heavy rain in Japan

> Live situation record from CLSTR: https://clstr.news/situations/weather-instability-and-heavy-rain-in-japan
> Updated: 2026-08-15T22:50:09.000Z. Sources: 3. Developments: 2.

In early August, the Japan Meteorological Agency issued heavy rain warnings for the Kanto and Koshin regions, forecasting up to 100 mm of rain within a 24-hour period. Authorities warned of potential flooding in low-lying areas, swelling rivers, landslides, and lightning.

By mid-August, weather conditions across Japan remained unstable. Following the Obon holiday, moist air from the south brought cloudy skies and sudden showers from Kyushu to Kanto. In Chiba Prefecture, where record-breaking heavy rains had recently occurred, officials warned that continued showers posed a landslide risk due to loosened ground. While cloud cover reduced the frequency of extreme heat days, high humidity persisted, with temperatures in parts of inland Kanto expected to exceed 35°C.

## Timeline

### 2026-08-15: Japan weather forecast predicts showers and humidity

Unstable weather and sudden showers are expected across Japan from Kyushu to Kanto, with continued landslide risks in Chiba and high humidity requiring heatstroke precautions.

3 sources. https://clstr.news/cluster/japan-weather-forecast-predicts-showers-and-humidity

### 2026-08-02: Heavy rain warning issued for Japan's Kanto‑Koshin region

Japan's Meteorological Agency warns of up to 100 mm rain in the Kanto‑Koshin area on Aug 2‑3, citing flood, landslide, lightning and hail risks.

2 sources. https://clstr.news/cluster/heavy-rain-warning-issued-for-japans-kantokoshin-region

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Cite as: Weather instability and heavy rain in Japan. CLSTR, https://clstr.news/situations/weather-instability-and-heavy-rain-in-japan