[UPDATE - Wednesday, May 24, 12.48pm]
At 12.30pm, the Hong Kong Observatory lowered the black rainstorm warning to an amber rainstorm warning.
A black rainstorm warning was issued by the Hong Kong Observatory on Wednesday after hours of rain drenched Hongkongers, slowing traffic to a crawl.
The signal means heavy rain has fallen or is expected to fall generally over Hong Kong, exceeding 70mm an hour, and is likely to continue.
The latest warning came after earlier alerts – an amber rainstorm warning at 6.40am, which was upgraded to a red signal at 9.15am.
All afternoon school classes have been suspended, the Education Bureau announced. Morning and whole-day schools which are in session should continue until the end of school hours.
The bureau urged schools to implement contingency measures to ensure the safety of students. Staff should also ensure conditions are safe before allowing students to return home.
The Social Welfare Department said all centres for child care, elderly services and day rehabilitation remained open. The public could contact the centres to arrange safe return home for their children and family members if necessary.
Thundery showers associated with a trough of low pressure are affecting the coastal areas of Guangdong.
Locally, more than 50mm of rainfall was recorded over many areas in Hong Kong on Wednesday morning, with rainfall exceeding 100mm in Kwai Tsing and Sham Shui Po.
A thunderstorm warning was also issued at 4.40am and will remain in force until at least 1pm.
The Observatory warned that there will be flooding in some low-lying and poorly drained areas.
The weather on Wednesday is expected to remain cloudy with occasional heavy showers and squally thunderstorms before it gradually becomes fine in the next few days.