Hong Kong has a "mature" mechanism that will be activated automatically to respond to inclement weather despite challenges in predicting rainfall, Chief Secretary Eric Chan said on Saturday.

Torrential rain pounded the city in recent weeks, prompting the Hong Kong Observatory to issue four black rainstorm warnings within a space of eight days. The fourth signal, issued on Tuesday, was up for more than 11 hours.

"I can honestly say that no one could have predicted the downpours would last this long, nor could anyone have predicted the rain's intensity," Chan told a Commercial Radio programme.

Chan also defended the government's decision not to hold a meeting of an inter-departmental committee that he chaired – which last convened to make preparations in response to Tropical Cyclone Danas in July.

The Emergency Monitoring and Support Centre, he said, will be up and running whenever a black rainstorm alert or a No 8 typhoon signal is in force.

"While we might not be able to predict rainfall sometimes, we have a response mechanism that can be up and running immediately," Chan said.

"This time proved that the existing mechanism was operating smoothly.

"I hope residents understand that not holding a meeting of the steering committee does not mean there was less protection."

The steering committee on handling extreme weather will meet and make advanced preparations when extreme weather conditions are expected to have a widespread and severe impact on the city, Chan added.