A landslide and flash flooding in nearby Rizal province killed 35 people, said provincial government spokesman Tony Mateo. Most of the fatalities in Rizal drowned, said Loel Malonzo, chairman of the Provincial Disaster Coordinating Council.
Three people were also reported killed in Manila's southern suburb of Muntinglupa and two others in Quezon city, said Anthony Golez, deputy presidential spokesman and acting head of the Office of Civil Defense.
Malonzo said that those who died did not live near creeks and were unaccustomed to flooding. "It has been about 40 years since something like this has happened here and many who migrated to the province were unfamiliar with the flooding," Malonzo said.
Mateo said that 27 people were missing.
President Gloria Macapagal Arroyo had to take an elevated commuter train to the disaster council office to preside over a meeting because roads were clogged by vehicles stuck in the floodwaters.
The mayor of Cainta, also in Rizal, who was stranded atop a dump truck on a road that was neck-deep in water, told ABS-CBN television by phone that many residents climbed onto roofs to escape.
"The whole town is almost 100 percent underwater," Mayor Mon Ilagan said.
About 16.7 inches (42.4 centimeters) of rain fell on metropolitan Manila in just 12 hours on Saturday, exceeding the 15.4-inch (39.2-centimeter) average for September, said chief government weather forecaster Nathaniel Cruz. The rainfall on Saturday also broke the previous record of 13.2 inches (33.4 centimeters), which fell during a 24-hour period in June 1967, he said.
"However good your drainage system is, it will be overwhelmed by that amount of rainfall," he told The Associated Press.
He said poor maintenance of drains and waterways clogged with garbage compounded the problem.
ABS-CBN television showed a dramatic video of more than a dozen people perched on roofs of damaged houses being swept away by the suburban Marikina River. They smashed against the pillars of a bridge and were separated from each other in the rampaging river. It was unclear whether they were rescued.
Cruz said seasonal monsoon rains were intensified by Ketsana, which packed winds of 53 mph (85 kph) with gusts of up to 63 mph (100 kph) when it hit land early Saturday. By the evening, the storm maintained its strength as it moved over the coast of western Zambales province and headed west toward the South China Sea.
Stranded residents called radio and television stations for help.
Popular actress Cristine Reyes tearfully appealed on ABS-CBN television from the roof of her two-story home, saying she and her mother and two young children had been waiting there for rescue for over six hours.
"If the rains do not stop, the water will reach the roof. We do not know what to do. My mother doesn't know how to swim," she said.
Manila airport operations chief Octavio Lina said the runway had been flooded, delaying international flights for hours. Floodwaters also caused some electrical outages.
Hundreds of vehicles were stalled in flooded streets around the capital, and nearly 2,000 passengers were stranded in ports in several provinces south of Manila after the coast guard suspended ferry operations.
The rains also caused the water in two dams near Manila to overflow, the national disaster agency said. It said water was waist-deep in some communities in northern Bulacan province near one dam.
Power distributor Meralco cut off electric service to some flooded areas in metropolitan Manila to prevent accidents, spokesman Joel Zaldarriaga said.