The city’s weather observatory issued the “red” signal before 6 a.m. local time, saying rain exceeding 50 millimetres in an hour is falling and likely to continue.

“Heavy rain will bring flash floods and flooding is occurring or expected to occur in watercourses,” it said.

Hong Kong’s stock market will remain open unless the highest “black” signal is issued.

The heavy rain comes as the city is still repairing damage caused by torrential rain linked to typhoon Haikui which passed nearby in recent days. Many areas of the mountainous city still have a high landslide risk after the unusually wet weather.

Some areas of the city such as Tsueng Kwan O and Sai Kung were still struggling with flooding from earlier in the week. A luxury house in the affluent Tai Tam area overlooking the ocean was ordered to be evacuated on Saturday due to risk of collapse.

Cascades of waist-deep water flooded the narrow streets of the former British colony and inundated malls, metro stations and tunnels, killing two people and injuring more than 144 last week.

(Reporting by Farah Master; Editing by Christopher Cushing)