Typhoon Santi, internationally known as Nari, pounded northern Luzon early Saturday, killing 13 people, ripping roofs off thousands of buildings, and leaving more than two million without power.
Santi tore into the country's northeast coast around midnight (1600 GMT Friday), toppling trees and pylons as it cut a westward swathe through the farming regions of the main island of Luzon, officials said.
"While there were relatively few casualties, a lot of areas are still flooded," said Eduardo del Rosario, head of the National Disaster Risk Reduction and Management Council.
Witnesses in the coastal town of Baler, near where Santi made landfall, said many large trees had been felled and clean-up crews with chainsaws were clearing roads.
Military and police rescuers trucked residents out of flooded villages as the weather improved after the typhoon's 120 kilometres (75 miles) per hour winds swept out to the South China Sea later Saturday morning.
Government clerk Glenn Diwa, 34, said she and her husband spent a sleepless night as the typhoon roared through the town of Capas, 90 kilometers (55 miles) north of Manila, shortly before midnight.
"The wind was very strong and there was a whistling sound. After a while we heard torn roofing sheets clattering across the yard," she told AFP.
As Santi dumped rain inland, a wall of mud fell on a police barracks near the town of Magalang, killing an officer awaiting deployment to rescue typhoon victims, the disaster council's spokesman Rey Balido told a news conference.
Elsewhere in central Luzon, an elderly woman and four minors were crushed to death when trees crashed onto two houses and a vehicle, while the wall of a school collapsed and crushed an old man to death.
Two children and an elderly person drowned in a flooded village, while the body of a fisherman who had gone to sleep in his boat on shore the previous night was recovered at sea, Balido added.
Another man was electrocuted by a loose power line while yet another died of a heart attack in an incident that disaster officials also blamed on Santi.
Three other fishermen who put to sea before the typhoon have also failed to return, Balido said.
He said nearly 6,000 people moved into government-run shelters amid warnings their communities could be hit by flooding and landslides from the typhoon.
A local news station aired footage of earth-colored floodwaters climbing above river defences and swamping farmland in San Miguel, where three of the victims had drowned.
Soldiers, police, and local government workers used military trucks to rescue residents in flooded communities in San Miguel and Minalin towns, the regional civil defence office there said.
"The wind picked up very quickly, very dramatically. We had the wind coming right off the ocean for four hours," said one witness on the east coast.
Even as the weather improved, floodwaters continued to rise in low-lying areas as rain from the nearby Sierra Madre mountains swept downstream through swollen rivers.
In the town of San Ildefonso, 60 kilometers from Manila, police pulled a woman on a motorbike and a farmer to safety after they were nearly swept away while separately crossing a street that had turned into a raging river.
Farmer Frankie Gracia, 30, told AFP he had been forced to butcher one of his pigs after it fell ill from exposure to the rain, and he had wanted to take some of the pork to his relatives across the street.
"I needed to reach the other side soon, otherwise the meat would spoil," he said.
Balido said 8,414 houses were damaged, while the central Luzon civil defence office said the typhoon blacked out 37 towns and cities, populated by 2.1 million people.
Road and utility crews were out clearing roads and restoring power, but it could take up to two days before electricity is restored and major highways are reopened to traffic, Nigel Lontoc, a disaster official for the region, told AFP by telephone.
The Philippines is hit by some 20 typhoons each year.
Santi is expected to be close to Vietnam's northeast coast by Tuesday, the Hong Kong Observatory said.