PAGASA has officially declared the onset of the rainy season following observed cumulative rainfall over the past five days brought by the southwest monsoon.

In a press release, the state weather bureau said the rains signify the start of the rainy season across the western sections of Luzon and the Visayas.

PAGASA Weather Specialist Rhea Torres noted in a weather forecast that despite the declaration, periods of “monsoon breaks” — or days and even weeks without rain — may still occur.

“Prepare your umbrellas or any rain gear, because rain is now possible not just in the afternoon, but also in the early morning or even at dawn,” Torres said.

Clouds from the southwest monsoon are currently affecting the western sections of Central Luzon, particularly Bataan and Zambales, as well as the Ilocos Region, Cordillera Region, and Metro Manila.

The remaining parts of Luzon are forecast to experience partly cloudy to cloudy skies, with isolated thunderstorms likely in the afternoon and early evening.

Over the next 24 hours, moderate to heavy rainfall — ranging from 50 to 100 millimeters — is expected in Bataan and Zambales, which could result in flooding and landslides.

A flood advisory has been issued for the tributaries of Morong and Balanga in Bataan, as well as Pamatawan, Sto. Tomas, Bucao, Bancal, and Lawis in Zambales.

Tomorrow, temperatures in Metro Manila are forecast to range between 25°C and 32°C, while Cebu can expect temperatures between 26°C and 32°C.