Why 14 inches of rain fell in Japan in just one day

This extreme rain was deadly, with at least eight people killed and many others stranded

By Jackie Flynn Mogensen edited by Claire Cameron

A figure walking in the rain as cars pass. — Cars pass a commuter on a flooded road near the Chiba metro station in Chiba, Japan, on August 13, 2026, as heavy rain sweeps through the area. Torrential rain pummeled eastern Japan, triggering landslides and power outages and prompting the country’s weather authority to issue its highest-level heavy rain warning for the region for the first time.

Philip FONG/Getty Images

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Record-breaking rain in Japan’s Chiba Prefecture, east of Tokyo, has killed at least eight people and sparked widespread power outages and travel disruptions, according to Japanese media reports.

In Chiba, the capital city of Chiba Prefecture, a total of 367 millimeters (about 14.4 inches) of rain fell in a 24-hour period ending on Thursday. This was the highest rainfall reading for that area since at least 1976, according to the Japanese Meteorological Agency (JMA), and represented more rain in a full day than has ever been recorded in many U.S. states. Incredibly, 348 millimeters fell in just 12 of those hours—about three times the typical amount of rainfall in the region for the entire month of August.

Thousands of travelers were stranded at Tokyo’s Narita International Airport, while tens of thousands of homes have lost power across the region, according to the Japan Broadcasting Corporation (NHK).

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The reason for all the rain was humid air flowing north from the southern part of the country and meeting a cold air mass some 6,000 meters (nearly 20,000 feet) above the island of Honshu, which has made the atmosphere “unstable,” JMA officials said at a press conference.

These extreme rainfall events can have lasting health costs, including exacerbating chronic disease, respiratory illnesses, mental health issues, and more, says Kai Chen, an environmental epidemiologist and director of the Yale Center on Climate Change and Health.

Fueling a cycle of extreme weather, climate change is making these events worse. “When you have warmer temperature in the air, the air holds more moisture,” Chen says. More moisture means more rain and more flooding.

“With the warming climate, we are seeing more and more [of] these intense and frequent extreme rainfall events happening,” he says.

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