It has already passed the USA territory of Guam, where it caused widespread flooding and power outages. The storm is expected to see some weakening as it enters Philippines but rainfall will be very heavy over these areas.
Almost 43 million people in the south-east Asian region could be affected, according to United Nations' Global Disaster Alert and Coordination System. Richard Gordon, its chairman, said: "We're anxious for the 10 million people in the Philippines living in the path of this destructive storm, including those who have been displaced several times due to the monsoon rains last July and August". The Pearl River Delta region, which includes Hong Kong and Macau, is among the most densely populated in the world.
A typhoon may bring widespread damage such as uprooted trees and damage to infrastructure, according to PAGASA's forecast. With more than 111 million residents, the most populous province of China will embrace the super typhoon on Sunday before it is expected to downgrade to a severe tropical storm next Monday.
It is now barreling across the Pacific Ocean with wind gusts of more than 178 mph an hour (287 kph).
As of Wednesday, Typhoon Mangkhut was carrying maximum sustained winds of 205km/h and gusts of up to 255km/h, according to the Philippine weather bureau.
Cathay Pacific Airways Ltd. encouraged passengers travelling this weekend to and from Hong Kong to re-book and the airline will waive the fees.
The strongest typhoon to hit the Philippines this year is threatening the farmlands in Northern Luzon just before the rice and corn harvest.
"We're anxious for the 10 million people in the Philippines living in the path of this destructive storm", said Richard Gordon, chairman of the Philippine Red Cross. Hong Kong had been bracing for a direct hit on September 12, but the typhoon warning was cancelled the morning of September 13, the Hong Kong Observatory announced, as forecasts tracked Mangkhut's path further south.
According to Hong Kong Observatory, Mangkhut will enter the South China Sea on Saturday.
The Observatory said it expected to issue the Strong Wind Signal, No. 3 around midday, a second-level warning. As the system continues to get close to the PAR i.e. the Philippine area of responsibility, it is likely to intensify even further into a Cat 5 Typhoon.