After destroying huge tracts of rice and killing at least 13 people in the Philippines, Super Typhoon Megi is heading towards China, where officials have warned the storm may be the worst to strike this year.
Projections show the storm is expected to avoid Vietnam on its way towards China, with the centre passing between Hainan island and Hong Kong.
On Monday, China's National Meteorological Centre urged local governments to make full preparations for extreme weather.
About 140,000 people have been evacuated from 15 cities on Hainan island since heavy rains reached the province on Friday, Xinhua, the official news agency, reported.
In the Philippines, thousands of people sheltered in evacuation centres as heavy rains fell on Tuesday, a day after Megi - known locally as Juan - struck the main island.
Schools were suspended in Manila and other parts of Luzon island amid fears of flash floods, while rescue workers tried to reach villagers stranded in remote areas that were cut off by the typhoon.
"A lot of people are still in danger here in Luzon, especially those areas where there is still rain," Perfecto P Penaredondo, a disaster management official, said.
Megi was a category 5 super typhoon that packed winds in excess of 250 kph as it struck northeastern Luzon shortly before noon on Monday.
Low death toll
The death toll appeared to have been minimised by the government's timely preparations for the storm. More than 7,000 people were evacuated and lorries were sent to help rescue and relief operations.
Alex Rosete, the national Red Cross spokesman, said four people were killed in Pangasinan province, three of them by a collapsed structure and the other by lightning.
Three other people drowned in a storm surge that hit the coastal town of Maconacon in Isabela province, which bore the brunt of the storm, Faustino Dy, the provincial governor, said.
Roads in and out of Isabela were blocked by collapsed trees, power lines and debris. Iron-sheet roofs on many of the houses were blown away.
The damage to rice and corn is still being assessed. According to an initial estimate, $36m worth of rice and corn crops were lost.
The crops were ready for harvest when the storm, the most powerful typhoon to hit the Philippines in four years, struck.
The Philippines is battered by an average of 20 typhoons a year, some of them deadly.
Tropical Storm Ketsana and Typhoon Parma struck the northern Philippine island of Luzon within a week of each other in September and October last year, triggering the worst flooding in recent history.
The twin storms killed more than 1,000 people, affected nearly 10 million and caused damage to $4.3bn of infrastructure and property, according to the World Bank and international humanitarian agencies.