Nagano issues record rainfall warning as 100mm falls in one hour

The Japan Meteorological Agency has issued a "record short-duration heavy rain" warning for the Ina area of Nagano Prefecture, citing an imminent risk of landslides and flooding. The alert follows radar analysis confirming that approximately 100 millimetres of intense rain fell in the region within the one-hour period ending at 7:10 pm local time on 27 July 2026.

Issued at 7:28 pm, the warning classifies the event under a specific category reserved for rainfall intensity that has historically caused significant damage in a short timeframe. The Japan Meteorological Agency highlighted that the speed and volume of the precipitation present a direct threat to public safety, prompting urgent advisories for residents in the affected zone.

This incident occurs against a backdrop of severe weather volatility across the country. On the same day, temperatures in Kyushu reached above 40 degrees Celsius for the first time since records began, while other regions grappled with different meteorological challenges. The juxtaposition of extreme heat and torrential rainfall underscores the complex weather patterns currently affecting Japan.

Similar warnings were deployed earlier in the day in other prefectures, indicating a broader regional instability. The Japan Meteorological Agency issued a "recorded short-duration heavy rain" warning for Nanto Town in Toyama Prefecture at 2:30 am, after 100 millimetres of rain were recorded in one hour. Additionally, a warning remained in effect for Itoigawa City in Niigata Prefecture until midnight.

In Niigata Prefecture, the situation remains critical with Level 4 Heavy Rain Warnings active for Nagaoka City, Kashiwazaki City, and Kariwa Village. These warnings represent the highest level of alert, indicating that serious disasters are already occurring or are highly likely. Authorities continue to monitor the situation as the immediate impact of the Nagano rainfall is assessed.