The Observatory said it will consider issuing the Standby Signal No 1 on Thursday night, as a tropical cyclone develops in the South China Sea.

But the agency said "persistent strong winds" were unlikely, as the cyclone would remain a considerable distance from Hong Kong.

It said a broad area of low pressure over central and northern South China Sea was expected to develop into a tropical cyclone, and come within 800km of the SAR on Thursday.

As it moves towards the seas south of Hainan Island, the storm could be closest to the SAR on Friday noon, skirting about 600km from the territory.

"Unless the tropical cyclone intensifies significantly or adopts a track closer to the coast of Guangdong, the chance of persistent strong winds generally over the territory is expected to be relatively low," the Observatory said.

It will be mainly cloudy with occasional showers and a few squally thunderstorms on Thursday and Friday, but sunny periods are possible over the weekend.