Heavy flooding and a city-wide red alert were issued by Hong Kong Observatory. Experts warn of increased landslide risks due to saturated soil from recent storms. Shenzhen also issued a red alert, reflecting regional extreme weather trends.
Daily Life in Hong Kong was thrown out of gear after the city recorded the highest single-day rainfall in August since 1884. As of 2 pm on August 5, the Observatory recorded 355.7 millimetres of rain, marking the highest amount of daily rainfall for the month of August since records began in 1884, according to the weather bureau’s website. Several flights were delayed and metro services were affected. Landslides were reported and a a city-wide red alert was issued for the first time since 2018. Last year, Hong Kong had recorded its hottest day of the year on August 5 with the Observatory logging a temperature of 35.4 degree Celsius.
Several areas, including the city’s financial hub, saw rainfall levels reach up to 400 millimetres between midnight and 2:15 p.m. The Observatory issued a black rainstorm warning early in the morning—its most severe alert level—indicating hourly rainfall exceeding 70mm. The warning remains in effect until at least 5 p.m.
Hong Kong International Airport has been significantly affected, with 361 flights delayed and 11 cancelled by 2:35 p.m., according to data from Flightradar24. The extreme weather has also caused severe flooding in multiple areas and triggered at least 13 landslides, including one on Po Shan Road in the upscale Mid-Levels area. That location was the site of a deadly landslide in 1972, which claimed 67 lives and prompted major reforms in slope safety management.
Commuters faced difficulties as some metro station exits were closed during the morning rush hour. The judiciary announced that all scheduled court proceedings would be postponed, and the Hong Kong Gold Exchange suspended its open outcry trading session for the day.
Geotechnical experts have raised concerns about the cumulative impact of recent rainstorms. Stuart Millis, associate director at Arup and an engineering geologist, told Bangkok Post that repeated bouts of intense rainfall can over-saturate soil and elevate groundwater levels, increasing the risk of slope failures and further landslides.
This week’s extreme rainfall follows an unusually dry start to the year, when precipitation levels were less than half the norm. Now, however, the region is experiencing frequent, powerful storms. Millis warned that the rapid succession of red and black rain warnings could have lasting effects on the city’s terrain stability.
Neighbouring Shenzhen issued a citywide red rain alert at 4 a.m. Tuesday—its first since 2018—as parts of mainland China continue to battle extreme weather. Over the past week, major cities such as Beijing and Shanghai have faced severe flooding and heavy rains.
Hong Kong’s most dramatic black rainstorm occurred in September 2023, when the warning remained active for 16 hours. That storm shattered multiple rainfall records, with 606 millimetres falling in just 12 hours—making it the heaviest on record. The resulting flooding submerged streets, inundated metro stations, and led to insurance claims totaling HK$1.5 billion (US$191 million).
Tuesday’s storm underscores the increasing frequency and intensity of extreme weather events in the region, highlighting the need for continued vigilance and robust infrastructure planning.