Record-breaking rainfall triggered widespread flooding and landslides across Fukui Prefecture in central Japan on Sunday, August 30, after more than 300 mm (11.8 in) of rain fell across several areas in just 24 hours.
At least 19 rivers overflowed across the prefecture as intense thunderstorms repeatedly crossed the same areas overnight. Roads and homes were inundated, vehicles became stranded and landslides cut transport routes through mountainous areas.
The Japan Meteorological Agency issued its highest-level Special Heavy Rain Warning for Fukui, Ono and Katsuyama at 04:30 local time, warning that rainfall of a magnitude rarely experienced in the region was occurring.
Las fuertes lluvias generan inundaciones en la ciudad de Fukui , Japón pic.twitter.com/a0GjepVUGn
— Alertageo (@alertarojanot) August 30, 2026
JMA said the situation corresponded to Alert Level 5, meaning that a disaster may already have been occurring and residents needed to take immediate action to protect their lives.
The warning remained in effect until 11:40, when it was downgraded. Authorities stressed that the danger did not disappear with the warning.
More than 350 mm falls in 24 hours
Rainfall totals illustrate the exceptional nature of the event.
Katsuyama recorded 350.5 mm (13.8 in) during its wettest 24-hour period, breaking its previous observational record of 197 mm (7.8 in) by a remarkable margin.
Miyama in Fukui City recorded 318 mm (12.5 in), while Harue in Sakai reached 314 mm (12.4 in). All three locations established new 24-hour rainfall records.
From the beginning of the rain event through 16:00 Sunday, accumulations increased further.
Fukui sedang dilanda banjir akibat hujan lebat ekstrem. Air terlihat menggenangi area permukiman dalam cukup luas. 🥲
— 𝑹𝒂𝒚𝒂𝒂🐈⬛🎀♡ (@wichurikuri) August 30, 2026
Semoga hujan segera mereda, air cepat surut, dan seluruh warga yang terdampak diberikan keselamatan serta perlindungan. Semoga keadaan di Fukui segera kembali…
Katsuyama reached 376.5 mm (14.8 in), Miyama recorded 343.5 mm (13.5 in) and Harue reached 341 mm (13.4 in).
In some locations, the rain that fell during the storm exceeded the amount normally expected during the entire month of August.
The extraordinary totals caused rivers and drainage systems to respond rapidly.
19 rivers overflow across Fukui
Authorities reported flooding along 19 rivers across Fukui Prefecture as runoff poured out of saturated hills and mountains.
Homes suffered both above-floor and below-floor flooding, while numerous roads disappeared beneath floodwater.
Katsuyama City activated its disaster response headquarters immediately after the Level 5 warning was issued. Officials reported damage to rivers, roads, irrigation channels and agricultural land as well as flooding beneath homes.
In Ono, a landslide struck National Route 158, illustrating the growing danger across the prefecture’s mountainous interior.
#JAPAN– Heavy rain warning issued for Fukui Prefecture, Japan. This footage from Omiyamachi, #Fukui City, was recorded around 4 a.m.
— Chaudhary Parvez (@ChaudharyParvez) August 30, 2026
Authorities are urging residents to take immediate action to protect lives.
pic.twitter.com/zRCw55TVTK
Across eight municipalities, emergency safety orders and evacuation instructions affected 159,234 households containing approximately 387,899 people.
The full extent of the damage was still being assessed Sunday afternoon.
Why did so much rain fall over Fukui?
The extreme rainfall developed as a frontal boundary stalled across the Hokuriku region.
Exceptionally warm and humid air flowed northward around the western side of the Pacific high-pressure system, transporting large quantities of moisture toward central Japan.
As this moisture encountered the front, air was forced upward and repeated cumulonimbus clouds developed.
Rather than one storm simply crossing Fukui and moving away, new areas of intense rainfall repeatedly formed and passed over similar locations. This allowed precipitation totals to accumulate extremely quickly.
Rainfall rates of around 50–60 mm (2–2.4 in) per hour were observed during the most intense periods.
Fukui’s terrain amplified the situation further. Moist air moving inland from the Sea of Japan encountered mountainous terrain, forcing it higher and enhancing precipitation through orographic lift.
The combination of a nearly stationary frontal zone, an abundant moisture supply and repeated convective development created an efficient setup for prolonged extreme rainfall.
Rain eases, but landslide danger remains
The most intense rainfall had largely subsided by Sunday afternoon as the low-pressure system associated with the rain moved eastward.
JMA lowered the Level 5 Special Heavy Rain Warning at 11:40, but significant hazards remained.
After more than 300 mm of rainfall, soils across the hardest-hit areas are extremely saturated. Landslides can therefore occur hours after the heaviest rain has stopped, while runoff from mountainous catchments can keep rivers elevated long after rainfall rates decrease.
Flooded roads and damaged infrastructure also complicate recovery efforts.
The August 30 storm has already entered Fukui’s meteorological record books. In several communities, more than a month’s worth of summer rainfall effectively arrived within a single day, transforming normally manageable rivers and streams into a widespread flood emergency.
