The Observatory raised typhoon signal No 3 at 4.15pm as Typhoon Rammasun edged closer to Hong Kong, bringing with it squally showers and gusts of wind up to 70km/h.
At 9pm, Severe Typhoon Rammasun was estimated to be about 520 kilometres south of Hong Kong and is forecast to move northwest at about 22km/h in the general direction of western Guangdong and Hainan Island, the Observatory said.
Thundery showers on Thursday night brought more than 20 millimetres of rainfall to parts of the territory.
On the present forecast track, the chance of issuing higher signals tonight is not high, the Observatory said.
When Rammasun moves to the southwest of Hong Kong and edges close to the south China coast later on Thrusday and on Friday morning, local winds on high ground and over southwest coastal region will occasionally reach gale force.
Hong Kong awoke on Thursday morning to a No 1 signal issued by the Observatory as wet and windy weather on the fringes of the typhoon brought some respite to days of stiflingly hot weather that has seen the city swelter.
Watch: Typhoon shuts down Philippine capital
Typhoon Rammasun killed at least 11 people as it passed across the Philippines and hit the capital Manila on Wednesday, prompting the evacuation of more than 370,000 people, shutting financial markets, offices and schools.
The eye of the typhoon, the strongest storm to hit the country this year, passed to the south of Manila on Wednesday after cutting a path across the northern island of Luzon.
Cathay Pacific said it had cancelled four flights from Manila to Hong Kong on Wednesday and a further two from Hong Kong to Manila. The airline advised passengers to check their flight status on its website before departing for the airport.
Last week, Typhoon Neoguri battered Okinawa in Japan before moving to the Japanese mainland and forcing the evacuation of tens of thousands.
At least seven people were reported to have been killed as mudslides and floods hit houses.
While Hong Kong has avoided any typhoons so far this year, the city has sweltered, with the hottest June since records began in 1884.
The monthly average was 29 degrees Celsius – 1.1 degrees above normal for June.
Johnny Tam, Danny Mok, Reuters