The Observatory lowered the Strong Wind Signal No 3 to the standby No 1 around 4am on Thursday, but officials warned of a worse threat from Super Typhoon Mangkhut.
The government said it is preparing to activate the Emergency Monitoring and Support Centre, ahead of potential direct hit from the powerful storm this weekend.
The Security Secretary, John Lee, chaired a cross-departmental meeting on Wednesday evening and said authorities will monitor the situation when Mangkhut arrives. Depending on conditions, the Security Bureau may escalate the emergency response level and activate the Emergency Monitoring and Support Centre.
The centre monitors and co-ordinates the response of the emergency and support services and provides help. It also briefs the Chief Executive and senior officials on developments and disseminates central government policy decisions and advice.
The Observatory says the storm, with winds of up to 240km/h, could be closest on Sunday.
A senior scientific officer at The Observatory, Lam Ching-chi, urged people to prepare for Mangkhut's arrival.
"As Mangkhut has a large circulation with intense winds, it will pose a considerable threat to the coast of Guangdong. Although there are still uncertainties in its track, Mangkhut is expected to bring adverse weather to Hong Kong, with frequent squalls and heavy rain, according to the present forecast track," Lam said.
"Seas will be very rough with swells, together with storm surges. Low-lying areas may have flooding or backflow of sea water."