The prevailing El Niño dry spell has delayed the onset of the rainy season by a week or two, weathermen said.
With about 60 per cent of the country in the grip of a dry spell since late last year, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (Pagasa) revised its forecast the rains would start by mid-June.
The rainy season usually starts between the last week of May and the middle of June, according to meteorologist Gener Quitlong. "But because of El Niño, the hot weather might extend up to the third week or end of June," he said.
"The southwest monsoon is not here yet," he added, referring to the wind system that brings rain during the so-called typhoon season.
The delay in the onset of the rainy season means the hot and humid weather felt the past three months will continue.
A ridge of high pressure is currently affecting northern and Central Luzon and will bring continued hot and humid weather to most of the country, according to Pagasa.
Quitlong said there were years when the rainy season was similarly delayed because of El Niño, which is characterized by unusually warm sea surface temperatures in the Pacific Ocean.
In the western Pacific where the Philippines is located, the phenomenon causes dry conditions, decreased rainfall and warmer air temperatures.
In a bulletin on June 3, Pagasa said that from October last year to May this year, 60 per cent of the country was affected by either drought or a dry spell.
In May, 80 per cent of the country received below to way below normal rainfall.
Pagasa forecast that in June, the rainfall would be back to almost normal in most of the Visayas and Mindanao, while many areas in Luzon, including Metro Manila, would likely receive below normal rainfall.
The agency warned that the current "weak" El Niño would begin to intensify to "moderate" strength in August and would last up to early next year.
As a result, the weather bureau said that from August to December, most parts of the country would get less than the usual rainfall that they receive during the rainy season.
"We are seeing the impact of a very dry condition from August onwards… In October we will feel the full impact of El Niño," climatologist Anthony Lucero had earlier said.
But Pagasa also said the country may expect to receive "ample" rain in June, with at least one to two typhoons expected to hit.
The weather bureau said the rainfall would start to decrease starting in July.
All dams are already below their normal operating levels, but not yet at their critical levels.