More than 40cm of rain fell on parts of Hong Kong over the last 24 hours, the Observatory said on Wednesday, delaying flights at the airport and closing schools.
The downpours came in short, sharp bursts, with the red rainstorm warning issued twice in six hours.
Heavy rain would continue to affect Hong Kong for the rest of the day, senior scientific officer Lee Lap-sun said.
“The trough of low pressure will continue to bring Hong Kong thundery showers tonight and early tomorrow,” Lee said. “The weather will not start to ease until late on Thursday.”
More than 400 flights were cancelled and delayed on Wednesday. The Airport Authority said that due to the inclement weather, 169 arrivals and 210 departures were delayed – and 15 arrivals and 13 departures were cancelled today.
According to Fire Services Department, there were three reports of floods between 12am and 5pm today.
The Observatory lowered the amber rainstorm warning at 3.55pm but warned residents to be aware of the danger of river flooding.
Early on Wednesday, the Observatory raised a thunderstorm warning at 2.50am and warned that gusts reaching 70km/h could affect Hong Kong. A landslip warning was issued at 11.40am.
An earlier red rainstorm signal forced schools to close for the day. Most schools in Hong Kong are now in the summer recess but some students still needed to go to added classes or special sessions to prepare for exams.
“Classes of all AM schools and whole-day schools are suspended today,” the government said.
“Schools should implement contingency plans and arrange staff to look after students who might arrive and ensure that conditions are safe before allowing students to return home.”
The Transport Department reported two traffic accidents this morning and congested traffic.
Red flags have been hoisted at a number of beaches, including Clear Water Bay Second Beach, Lo So Shing Beach, Pui O Beach, Lower Cheung Sha Beach and Tong Fuk Beach. Authorities have advised visitors not to go swimming due to large waves.
Temporary shelters are also being set up around the city. The Home Affairs Department said that up to 62 shelters may open during the rainstorm based on request, with 10 on Hong Kong Island, six in Kowloon and 46 in the New Territories. Residents can phone in their requests for shelter to 2835 1473.
Further heavy showers and squally thunderstorms are forecast for the rest of Wednesday and on Thursday morning. Showers are expected to ease off on Thursday afternoon.
Additional reporting by Michelle Toh, Clifford Lo and Lai Ying-kit