The observatory issued the Standby Signal No 1 at 11.20am on Monday, as Severe Tropical Cyclone Rai came within 800 kilometres of Hong Kong.
The storm has weakened since causing havoc and deaths as it passed over the Philippines at the end of last week. It’s expected to weaken further as it moves across the central part of the South China Sea.
Hong Kong forecasters warned there could be strong winds over offshore waters and on high ground.