Hong Kong records highest August daily rainfall since 1884, four black warnings in 8 days
Hong Kong recorded its heaviest August daily rainfall since records began in 1884, with 355–359 mm (14–14.1 inches) measured by mid‑afternoon on August 5, 2025, prompting a black rainstorm warning that lasted more than 11 hours, the second‑longest on record.
Image credit: Kyle Lam/HKFP
The Hong Kong Observatory (HKO) reported 355.7 mm (14 inches) of rainfall at its Tsim Sha Tsui headquarters by 14:00 local time (LT) on August 5. Later readings reached 358.8 mm (14.1 inches), surpassing all previous August daily rainfall records since observations began in 1884.
The black rainstorm warning, issued when hourly rainfall exceeds 70 mm (2.8 inches), remained in force for approximately 11 hours and 15 minutes, second only to the 16.5‑hour warning issued in September 2023.
The August 5 event marked the fourth black rainstorm warning in just eight days, setting a new annual frequency record.
Rainfall rates peaked near 90 mm/hour (3.5 inches/hour), accompanied by over 9 600 lightning strikes recorded from 05:00–12:00 LT.
Severe flooding occurred in multiple districts. Queen Mary Hospital reported ankle‑deep water at entrances, forcing temporary service suspensions. The Drainage Services Department confirmed at least 25 flooding incidents, including submerged parking lots and flooded staircases.
Schools, courts, and outpatient clinics closed for the day. Traffic restrictions were imposed on the Hong Kong–Zhuhai-Macau Bridge, a span of 55 km (34 miles) due to low visibility. At Hong Kong International Airport, approximately 20% of flights were cancelled and more than 400 were delayed.
Meteorologists attributed the event to a low‑pressure trough interacting with the southwest monsoon, creating persistent heavy rainfall across the Pearl River Delta.
I’m a science journalist and researcher at The Watchers, contributing to the Epicenter edition, where I cover peer-reviewed scientific research and emerging discoveries across Earth and space sciences. With a background in astronomy and a passion for environmental science, I’ve worked in shark and coral conservation in Fiji, conducting reef and shark-behavior research, contributing to mangrove restoration, and earning PADI Open Water and Coral Reef Certifications. I bring a blend of scientific rigor and storytelling to illuminate the discoveries shaping our planet and beyond.
Commenting rules and guidelines
We value the thoughts and opinions of our readers and welcome healthy discussions on our website. In order to maintain a respectful and positive community, we ask that all commenters follow these rules.