QUEZON CITY — The southwest monsoon is tightening its grip on Luzon this Monday, August 11, 2025, pushing heavy to intense, at times torrential, rains into several western and central provinces and raising the risk of flash floods and landslides, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) warned in its 4:00 AM forecast bulletin, valid until 4:00 AM Tuesday.
While the rest of the country — the Visayas, Mindanao, and the eastern portions of Luzon — faces a calmer weather picture of partly cloudy to cloudy skies with only isolated showers, residents in the monsoon's direct path are urged to stay alert and avoid flood-prone and landslide-susceptible areas throughout the day.
What Is Driving Today's Weather
The main actor today is the southwest monsoon, known locally as habagat. It is a seasonal wind system that blows moisture-laden air from the South China Sea and the West Philippine Sea toward the Philippine landmass, typically from June through September. When this moist, warm air is forced upward by the mountains of Luzon's western seaboard — the Zambales and Bataan ranges, among others — it cools rapidly and releases heavy rainfall, often in bursts intense enough to cause flooding within a short period.
PAGASA also notes that Tropical Storm Peilou is currently located approximately 3,255 kilometers east of extreme northern Luzon, at coordinates 27°N, 117°E, and is moving east-northeastward at 25 kilometers per hour. With maximum sustained winds of 65 km/h near the center and gustiness of up to 105 km/h, Peilou is outside the Philippine Area of Responsibility (PAR) and is not directly causing rainfall over the country today. PAGASA is monitoring its movement.
Region-by-Region Forecast
Luzon: Monsoon's Frontline
The harshest conditions today will be felt in the provinces most directly exposed to the habagat. Zambales, Bataan, and Occidental Mindoro are under the heaviest impact, with PAGASA forecasting heavy to intense, at times torrential, rains with frequent thunderstorms. These are the conditions most strongly associated with flash floods and landslides, and residents — especially those living along riverbanks, in low-lying barangays, or on slopes — should be prepared to evacuate quickly if local authorities give the order.
A second tier of affected areas faces cloudy skies with scattered to widespread rains and thunderstorms. This covers a broad swathe of central and southern Luzon: Metro Manila, CALABARZON (Cavite, Laguna, Batangas, Rizal, Quezon), Pangasinan, Benguet, Tarlac, Pampanga, Nueva Ecija, Bulacan, Marinduque, Oriental Mindoro, and Camarines Norte. Moderate to heavy rainfall is possible in all of these areas, and flash floods or landslides may occur, particularly in mountainous and flood-prone zones. Commuters in Metro Manila and surrounding provinces should brace for disrupted travel.
The rest of Luzon — areas not specifically named above — can expect partly cloudy to cloudy skies with only isolated rain showers or thunderstorms caused by the southwest monsoon. While these conditions are significantly less severe, PAGASA still cautions that flash floods or landslides remain possible during any severe thunderstorm episode.
Visayas: Localized Storms Possible
The Visayas is outside the direct influence of the southwest monsoon today. PAGASA forecasts partly cloudy to cloudy skies with isolated rain showers or thunderstorms driven primarily by localized thunderstorm activity. While the overall weather picture is less threatening than in Luzon, these isolated systems can be intense and develop quickly. Flash floods or landslides remain a possibility if a thunderstorm becomes severe over a particular area.
Mindanao: Mostly Fair, Isolated Showers
Mindanao shares a similar forecast with the Visayas today — partly cloudy to cloudy skies with isolated rain showers or thunderstorms associated with localized thunderstorms. Residents should not be entirely off guard, as short but heavy bursts of rain are possible, but the overall threat level is considerably lower than in the monsoon-exposed parts of Luzon.
Wind and Sea Conditions
The monsoon's wind signal is clearest over the seas closest to its source. The northern and western sectors of Luzon will see moderate to strong winds blowing from the southwest, producing moderate to rough seas with wave heights ranging from 1.2 to 2.8 meters. These conditions are dangerous for small boats and bancas, and PAGASA implicitly cautions against venturing out in these waters.
The rest of Luzon can expect light to moderate winds and slight to moderate seas. Across the Visayas and Mindanao, light winds and slight to moderate seas are forecast, making conditions more manageable for maritime activity in those areas.
Decoding Today's Weather Warnings
PAGASA's forecast for Zambales, Bataan, and Occidental Mindoro describes "heavy to intense, at times torrential" rainfall — language that corresponds to conditions that can trigger rapid-onset flooding and landslides in a matter of minutes to hours. If you live in or near these provinces, take the warning seriously: do not wait for water to rise before acting. For the broader area covering Metro Manila and the named central Luzon provinces, "scattered to widespread" rains with thunderstorms means flooding of streets and low-lying areas is likely at various points during the day, not just once.
No formal tropical cyclone wind signal is in effect over any part of the country today, as Tropical Storm Peilou remains far outside Philippine territory. There is no gale warning or coastal warning beyond the wind and wave advisory for the northern and western Luzon seaboard described above.
To better understand the meaning of different PAGASA warning levels and what each requires of you, read our guide on how to read PAGASA's weather warnings.
What It Means for You
Commuters — Metro Manila and Nearby Provinces
Metro Manila, Bulacan, Cavite, Laguna, Rizal, Pampanga, and neighboring provinces are all in the zone of scattered to widespread rains. Expect flooded underpasses and intersections, particularly during and shortly after heavy downpours. Leave earlier than usual, keep an eye on traffic advisories from the MMDA and your local government, and carry rain gear. Avoid flood-prone roads even if rain appears to have stopped — water upstream can still surge downward.
Fisherfolk and Small-Boat Operators
If you operate a small vessel in the northern or western seas of Luzon, today is not a safe day to head out. Moderate to rough seas with strong southwest winds pose a serious hazard to small boats and bancas. Fisherfolk in the Visayas and Mindanao face calmer seas but should remain vigilant for sudden squalls associated with localized thunderstorms.
Farmers
Heavy to intense rainfall in Zambales, Bataan, Occidental Mindoro, and neighboring provinces can damage standing crops and cause soil erosion. Farmers in these areas should assess drainage and secure equipment. Those in areas receiving only scattered showers may benefit from the moisture but should watch for waterlogging in low-lying fields.
Students, Parents, and Schools
Schools in Zambales, Bataan, Occidental Mindoro, and the broader Metro Manila area should monitor local government advisories closely. The combination of heavy rain and flash-flood risk may prompt class suspensions. Parents should plan ahead and maintain communication with schools throughout the morning hours when rainfall is often at its heaviest.
Outdoor Workers and Construction Sites
Workers exposed to the elements in the monsoon-hit provinces face the highest risk today. Construction sites, quarries, and outdoor operations in Zambales, Bataan, Batangas, Laguna, and other affected areas should implement rain safety protocols and be ready to halt work if conditions deteriorate. Lightning from frequent thunderstorms is an added hazard.
Temperature Outlook
PAGASA's overnight observations at the Ninoy Aquino International Airport weather station recorded a maximum temperature of 29.5°C at 5:00 PM and a minimum of 24.4°C at 6:00 AM. Relative humidity peaked at 87% and dropped to a minimum of 71% at 2:00 PM, reflecting the muggy, overcast conditions the monsoon brings. Expect similar sticky, humid conditions across Metro Manila and the western Luzon corridor today, with temperatures moderated slightly by persistent cloud cover and rainfall.
Astronomical and Tidal Notes
Sunrise today is at 5:50 AM and sunset at 6:21 PM. The moon rises at 5:03 PM with a tidal prediction low of 0.12 meters at the same time, and the moon is at 2% illumination — a near-new moon. The nearly moonless night tonight means reduced natural light after sunset, an additional consideration for evening commuters and those traveling in rural, flood-prone areas.
Bottom line: If you are in Zambales, Bataan, Occidental Mindoro, Metro Manila, or any of the named central Luzon provinces, prepare for heavy to widespread rain today — do not enter flooded areas, move away from slopes and riverbanks at the first sign of heavy rain, and keep tabs on your local government's flood and class-suspension advisories. The rest of the country faces isolated showers only, but no one should dismiss a developing thunderstorm.
Monitor official PAGASA updates at pagasa.dost.gov.ph.