The weather warning was issued at 6.40am. The station has considered downgrading the signal waning to No. 3 for several times throughout the day.
At 7pm, Tropical Storm Lionrock was centered about 520 kilometers west-southwest of Hong Kong and is forecast to move northwest slowly into Beibu Wan.
The broad outer rainbands associated with Lionrock are affecting the vicinity of the Pearl River Estuary and are expected to persist for some time.
Strong to gale force winds will continue to prevail over the city under the influence of the rainbands,. There will also be occasional storm force winds on high ground over the southwestern part of the territory.
The public should continue to take precautions against flooding, stay away from the shoreline and not to engage in water sports.
Britain's Queen Elizabeth carried out her first official engagement on Tuesday since spending a night in hospital and being ordered to rest by her doctors.