Hong Kong will continue to face occasional showers and squally thunderstorms on Friday and Saturday, according to the observatory.

The weather agency said it recorded more than 100 millimetres of rainfall over many places in the SAR on Thursday, with repeated amber and red rainstorm warnings during the day. Rainfall exceeded 140 millimetres in some areas.

Shum Chi-tai, an acting senior scientific officer at the observatory, said the remnant of tropical storm Danas is not the only factor causing the unstable weather.

"The adverse weather is not related solely to the remnants of Danas, but also the southwest monsoon. From what we see, we expect that occasional showers and squally thunderstorms will continue, and there will be some more showers tomorrow," he said on an RTHK programme on Friday.

"Looking ahead, there will be an anticyclone aloft that will gradually affect Hong Kong in the coming days. Therefore, by early next week, the showers will let up and conditions will improve."

The Drainage Services Department confirmed six flooding reports between Wednesday night and 8am on Friday, with all of them coming from the New Territories.

Chan Hak-keung, the department's acting assistant director of operations and maintenance, said there was a flood on the San Tin Highway, two on San Tin Tsuen Road, and one each in Tai Wo Village in Pat Heung and Long Tin Road in Yuen Long.

"These six locations are not flooding black spots. What happened was that mud and silt, as well as tree leaves and branches were washed into drainage inlets and roadside gullies and caused blockages. After removal works were completed, the drains were up and running again within an hour or two," he told the same radio show.

Chan said more than 100 emergency response teams were dispatched to handle floods and clear blocked drains.

He added that before downpours on Wednesday, his department carried out inspections and clearance work at 240 spots across the city that are prone to flooding.