Typhoon Mangkhut, which has already flown through the Northern Mariana Islands and Guam, is accelerating across the Pacific with winds that can gust up to 255 kilometers per hour.
Authorities said some 10 million people in the Philippines are on the path of the storm, not including millions more on the densely populated coast of China.
Thousands began evacuating in the coastal areas of the northern tip of the main Philippine island of Luzon, where the storm is expected to make landfall early Saturday.
"We're really scared, they say (the typhoon) is so strong," said Delaila Pasion, who had fled her home. "We were too scared to stay."
"During the previous monsoon rains, half of our house was destroyed, so I wanted to take my grandchildren to a safe place," he told reporters.
Floods, landslides and wind damage from the next storm were the main concerns as authorities prepared teams for rescue and relief operations.
The schools were closed and some farmers were taken to their fields to begin the early harvest of corn and rice that could be ruined by the floods.
Typhoon Mangkhut hits Philippines and Guam
& # 39; Considerable threat & # 39;
An average of 20 typhoons and storms hit the Philippines each year, killing hundreds of people and leaving millions in near-perpetual poverty.
The deadliest in the country in history is the Super Typhoon Haiyan, which left more than 7,350 people dead or missing in the center of the Philippines in November 2013.
The state meteorological service said Mangkhut will be the strongest typhoon so far this year, with sustained winds of 205 kilometers per hour.
The typhoon is expected to increase the intensity of seasonal monsoon rains that have already caused flooding in central Luzon, a mainly agricultural region north of the capital, Manila.
The poor communities that depend on fishing are some of the most vulnerable to the fierce typhoon winds and the storm surge that hits the coast.
"It will bring destruction, they are the most affected, even moderate winds can tear down their houses," regional civil defense official Dante Balao told AFP.
Hong Kong is also targeted by Mangkhut and preparations have already started on Thursday, although the storm was not expected to arrive until Sunday.
Social media users and radio commentators from Hong Kong said they were supplying food and supplies.
The Hong Kong Observatory warned residents to prepare for the storm, saying it represented a "considerable threat".
The Philippine state meteorological service said heavy rains and strong winds are expected from Friday over northern and central Luzon, along with rough seas on the coasts.
The International Federation of Red Cross and Red Crescent Societies said it expected "substantial damage" on the Philippine road to Mangkhut.
Tides of up to seven meters are expected to increase in coastal areas, he said, while heavy rains could trigger landslides and flash floods.
The civil defense office in Manila said that towns and cities on the Mangkhut road are preparing government buildings such as evacuation centers, food storage and other emergency rations.