"Even further strengthening is expected with Mangkhut as it moves westward toward land", said AccuWeather Senior Meteorologist Adam Douty, adding, "If sustained wind speeds of 220 km/h are reached, Mangkhut will not only be a super typhoon, but also equivalent to a Category 5 hurricane in the Atlantic and eastern Pacific".
The strong winds generated by Mangkut could cause storm surge and heavy rain could trigger landslides and floods.
Mangkhut has already swept past the U.S. territory of Guam, in the western Pacific, where it caused flooding and power outages.
Cagayan Governor Manuel Mamba said by telephone that northern coastal and island villages in the typhoon's projected path will begin evacuating residents on Thursday ahead of the expected onslaught.
Schools were shuttered and some farmers took to their fields to start early harvest of corn and rice that could be ruined by flooding.
Emergency workers have been deployed in the northern tip of the main Philippine island of Luzon, where Typhoon Mangkhut is expected to make landfall on Saturday.
It is now barreling across the Pacific Ocean with wind gusts of more than 178 mph an hour (287 kph). Cathay Pacific encouraged passengers travelling this weekend to and from Hong Kong to re-book and the airline would waive the fees.
It was the most powerful storm to hit Japan in 25 years and left at least 11 people reported dead and more than 600 injured, cutting off power supplies to more than a million homes.
The typhoon is expected to boost the intensity of seasonal monsoon rains that have already caused widespread flooding in central Luzon, a mainly farming region north of capital Manila.
"As Mangkhut has a large circulation with intense winds, it will pose considerable threat to the coast of Guangdong", according to the Hong Kong Observatory.
The government, however, said it would remain on high alert and would be prepared for any changes in direction.
An average of 20 typhoons and storms lash the Philippines each year, killing hundreds of people and leaving millions in near-perpetual poverty. In 2013, Super Typhoon Haiyan which packed winds of as high as 315 kilometers per hour killed more than 6,300 people there.
The storm's current path has it passing through the Luzon Strait between the Philippines and southern Taiwan, before continuing on to Hong Kong and Macau.