Typhoon Koppu hit the northern Philippines killing at least two people and forcing tens of thousands from their homes.
Heavy rain and floods are affecting dozens of villages.
Troops have been deployed to help residents trapped on rooftops, but are struggling to access more remote areas.
Koppu has now been downgraded to a severe tropical storm by the Japanese Meteorological Agency, which is responsible for naming and tracking it.
However, the Philippines’ own weather agency, which calls the weather system Lando, is still characterizing Koppu as a typhoon.
Despite weakening, Koppu is expected to keep dumping rain on the country for a considerable time to come. Some forecasts suggest it may not be until October 21 that it moves past the Philippines and on to Taiwan.
Typhoon Koppu made landfall near the town of Casiguran on the main island of Luzon on October 18, bringing winds of close to 124mph and cutting power to vast areas.
A teenager was killed by a fallen tree in Manila which also injured four others. A concrete wall also collapsed in the town of Subic, northwest of Manila, killing a 62-year-old woman, officials said.
On October 19, wind speeds were down to 93 mph in the northern town of Santiago, according to the state weather service.
However, floodwaters are preventing even military vehicles reaching many of the worst-hit villages, and rescuers report a shortage of boats.
“We haven’t reached many areas. About 60% to 70% of our town is flooded, some as deep as three meters,” said Henry Velarde, vice mayor of Jaen, a town in Nueva Ecija province.
“There are about 20,000 residents in isolated areas that need food and water.”
While the Philippines is no stranger to typhoons and tropical storms, the slow-moving nature of Koppu means heavy rain will fall for longer than usual, bringing greater risk of flooding and landslides.
Typhoon Koppu is the second strongest storm to hit the Philippines in 2015.