The Hong Kong Observatory issued a black rainstorm signal on Saturday morning, the second one to go out this year, while warning the public to brace for possible flash floods.

The highest-level rainstorm signal was issued at 9.45am, escalating from the red rainstorm warning sent less than an hour earlier.

It means that heavy rain has fallen or is expected to fall generally over Hong Kong, exceeding 70mm in an hour, and is likely to continue.

“A band of intense thundery showers associated with an active southwest monsoon is affecting the vicinity of Pearl River [Delta],” the forecaster said.

“Rain is particularly heavy in Hong Kong Island’s Eastern district, with heavy rain of more than 70mm an hour falling, which may cause serious flooding.