Flash flood has paralysed metro stations and trapped drivers on roads, forcing authorities in Hong Kong to suspend schools.

Photos and videos showed residents wading through murky brown floodwaters as heavy rain continued to inundate the densely populated city of 7.5 million, reports CNN.

Authorities reportedly rescued riders stuck in their vehicles after streets were transformed into surging torrents in some low-lying areas.

The deluge began late Thursday night, with the Hong Kong Observatory recording more than 158 millimeters (6.2 inches) in rain between 11 p.m. and midnight, the highest hourly rainfall since records began in 1884, the government said in a news release as quoted by CNN.

The rain occurred just days after Hong Kong was lashed by the strongest typhoon in five years.

Typhoon Saola, originally a super typhoon, weakened to the equivalent of a Category 2 hurricane as it reached Hong Kong last weekend – but was still potent enough to shut down the city and cause hundreds of flight cancellations, reports CNN.