The Observatory said it will consider issuing the Standby Signal No. 1 between Wednesday night and early Thursday as a tropical depression is expected to enter within 800 kilometres of Hong Kong.

The forecaster said the tropical depression will move across the vicinity of Luzon on Tuesday and Wednesday, and is expected to move in the general direction of the coast of Guangdong and intensify gradually.

The Observatory said there are still uncertainties in its movement and intensity due to the influence of the northeast monsoon.

"As its circulation is relatively small, the tropical cyclone will only bring significant impact to local weather when it gets relatively close to Hong Kong," the Observatory said.

The forecaster added that it will access the need for issuing higher signals on Friday.

It said the weather will become unsettled on Friday, with stronger winds along with showers and squally thunderstorms over the weekend.