Heavy monsoon rain continues to threaten western Luzon in the Philippines on Tuesday, August 18, with the country’s weather agency placing several areas under its highest rainfall warning level.
PAGASA’s 2 p.m. bulletin placed Bataan, parts of Batangas and southern Zambales under a Red rainfall warning, indicating that serious flooding is expected in vulnerable areas.
Heavy Rainfall Warning No. 15 #NCR_PRSD
— PAGASA-DOST (@dost_pagasa) August 18, 2026
Weather System: Southwest Monsoon (Habagat)
Issued at: 2:00 PM, 18 August 2026(Tuesday)
RED WARNING LEVEL: Bataan, Batangas(Lian, Tuy, Calaca, Balayan, Calatagan, Agoncillo, Alitagtag, Batangas City, Bauan, Cuenca, Lemery, Mabini, San… pic.twitter.com/Q6jSn2Xg2i
Orange warnings covered additional areas, while Metro Manila and surrounding provinces remained under lower-level rainfall warnings as another moisture-rich period continued across Luzon.
Torrential rains have triggered severe flooding in Manila, Philippines on August 17 as the monsoon season reaches its peak. Authorities have been working overtime to rescue those trapped and assisting those in need. Monsoon season in the Philippines typically runs from June to… pic.twitter.com/3n3E4TvKjo
— TRT World (@trtworld) August 18, 2026
The renewed warnings come one day after torrential rain caused severe urban flooding around Metro Manila. PAGASA’s Science Garden recorded 201.7 mm (7.9 in) in only five hours on Monday, illustrating how efficiently the current atmosphere is producing rainfall.
BAHA SA PUERTO GALERA
— GMA News (@gmanews) August 18, 2026
Rumaragasa ang abot-binti na baha sa Puerto Galera, Oriental Mindoro bandang 10 AM ngayong Martes, August 18, 2026 dahil sa tuloy-tuloy na pag-ulan na dala ng Habagat.
Ayon kay YouScooper Roween Julius, patuloy pa rin ang pag-ulan at ang pagragasa ng tubig… pic.twitter.com/HmOzsdjYN1
Habagat Continues to Feed Rain Into Luzon
The driving force is the southwest monsoon, locally known as Habagat.
During an active Habagat pattern, persistent southwesterly winds transport warm, moisture-rich maritime air from the seas west and southwest of the Philippines toward Luzon.
That moisture is currently converging across western sections of the island, allowing rainbands and thunderstorms to repeatedly regenerate rather than simply moving through once.
This repeated rainfall is particularly important because the ground and urban drainage systems are already responding to Monday’s deluge.
Where successive rainbands follow similar paths, rainfall can accumulate extremely quickly. The process resembles thunderstorm “training,” with multiple areas of heavy precipitation crossing the same corridor.
Terrain Can Further Enhance the Rain
Western Luzon’s geography can intensify the effect.
Moist southwesterly winds reaching mountain ranges near the western coast are forced upward. As the air rises, it cools and condenses, enhancing precipitation through orographic lift.
This makes Bataan and Zambales particularly exposed during strong Habagat episodes.
PAGASA’s flood monitoring also shows flood watches affecting major river basins, including the Pampanga basin and the NCR/Pasig-Marikina-Laguna de Bay system.
With additional monsoon rain expected, the principal hazards remain rapid urban flooding, overflowing waterways and localized landslides in mountainous terrain.
The combination of an exceptionally moist atmosphere, persistent southwest flow and already wet catchments means further flooding can develop quickly wherever the strongest rainbands become established.
