According to the U.N. Global Disaster Alert and Coordination System, the super typhoon could affect as many as 43.4 million people before it fades away. 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". Mangkhut has already passed over Guam where power outages and torrential wind and rain impacted the small island.
It said there could be storm surges of up to seven metres (23ft) in coastal areas and that heavy rains could spark landslides and flash floods. Category 5 hurricanes, according to the Saffir-Simpson scale, have 157 miles per hour or greater winds.
The Philippines' state weather service says it will be the country's strongest typhoon this year, with winds peaking at 168mph on Thursday before easing slightly as it hits land. It was expected to leave the Philippine area of responsibility (PAR) by Tuesday morning.
Mangkhut is now barrelling across the Pacific with gusts of 255 kilometres (160 miles) per hour.
In the Philippines, 10 million people are living in the path of the powerful cyclone, according to the Red Cross which has placed its teams in Northern Luzon on alert.
A super typhoon with 230 km/h winds is brewing in the Pacific and heading to Hong Kong
Multiple Hong Kong airlines, including flag carrier Cathay Pacific, have announced they will waive charges for rebooking or re-routing flights arriving or departing the city during the worst of the storm.
The strongest typhoon to hit the Philippines this year is also threatening 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. According to HKO, the storm is expected to skirt around 100 to 200 kilometers (62 to 124 miles) south of Hong Kong on Wednesday afternoon, bringing strong winds and rain.
Mangkhut would be the 15th storm to batter the Philippines this year.
It could be felt strongest in the provinces of Cagayan and Batanes with an intensity of 205 to 255 kph.