Tropical Storm Ketsana triggered the worst flooding in decades in the capital Manila and nearby provinces.
Defence Secretary Gilbert Teodoro said troops, police and civilian volunteers had rescued more than 4,000 people - many clinging to each other on roofs.
More than 250,000 have been driven from their homes, officials say.
Military chief Gen Victor Ibrado flew by helicopter over suburbs of Manila on Sunday to see for himself drenched survivors marooned on top of half-submerged buses and on rooftops.
TV footage showed some survivors clinging to high-voltage power lines.
Correspondents say the rescue effort is intensifying as the weather cleared on Sunday.
But some reports estimate that 80% of the capital is still under water.
The government has declared a "calamity" in Manila and 25 provinces, allowing access to emergency funds.
Latest confirmed figures say that 73 people are dead and at least 23 others are missing.
One report puts the number of dead and missing at 106.
Manila bus driver George Andrada said he had lost everything in the floods.
"It happened very fast. All of a sudden everything was under water. I was not able to save anything except the shirt I am wearing," he said.
Some residents have emailed the BBC with their experiences. Lovely Lansang in Marikina, near Manila, says: "I am currently seeking refuge in a shopping centre. Many people are stuck either on their roofs or in the second storey of their houses.
"The city is also without clean water and electricity. Right now, I am still in the shopping centre because the roads here are impassable," the email adds.
The equivalent of a whole month`s rain fell in six hours as Ketsana, also known as Ondoy, lashed the northern island of Luzon.
On Saturday, TV images showed gushing water turning roads into rivers, with floods chest-deep a