QUEZON CITY, September 21, 2026 — Filipinos across all three major island groups should prepare for scattered thunderstorms on Monday as the southwest monsoon tightens its grip on western Southern Luzon and localized storm activity keeps the rest of the country under cloudy, unsettled skies, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) said in its 4:00 AM forecast issued today.
The forecast is valid for 24 hours, until 4:00 AM on Tuesday, September 22, 2026. While no tropical cyclone is currently affecting the country, PAGASA cautioned that severe thunderstorms — wherever they develop — can still trigger dangerous flash floods and landslides, making preparation and situational awareness critical for communities nationwide.
What Is Driving Today's Weather
The primary weather driver named by PAGASA today is the southwest monsoon, known locally as habagat. The habagat is a seasonal wind pattern that draws warm, moisture-laden air from the southwestern seas — the South China Sea and surrounding waters — into the Philippines, typically from June through September. When this moisture-heavy air pushes inland and meets terrain or rising heat, it releases that moisture as heavy rain, often with thunder and lightning.
Today, PAGASA says the habagat is directly affecting the western section of Southern Luzon, meaning the provinces closest to the South China Sea are receiving the most organized and consistent rainfall from this system. For the rest of the country — including Metro Manila, the Visayas, and Mindanao — PAGASA attributes the expected rainshowers and thunderstorms to localized thunderstorm activity, which means individual storms forming from heat and atmospheric instability rather than being organized by the monsoon itself. These localized storms can be brief but intense.
Region-by-Region Forecast
Luzon
The southwest monsoon is most directly felt across Palawan, Occidental Mindoro, and Oriental Mindoro, where PAGASA forecasts partly cloudy to cloudy skies with isolated rainshowers or thunderstorms throughout the day. Residents in these provinces should be on alert for sudden, heavy downpours that could cause flooding in low-lying areas and landslides on hillsides and mountain slopes.
Metro Manila and the rest of Luzon — including Northern Luzon provinces such as Ilocos Norte, Ilocos Sur, La Union, Pangasinan, the Cordillera Administrative Region, Cagayan Valley, and Central Luzon — are under the influence of localized thunderstorm activity. Expect partly cloudy to cloudy skies, with isolated rainshowers or thunderstorms that may develop quickly, especially during the afternoon and early evening hours when surface heating is strongest.
Wind conditions across Northern Luzon and the eastern sections of Central and Southern Luzon are notably stronger today. PAGASA describes winds in these areas as moderate to strong, blowing from the northeast to northwest direction. This is the most hazardous wind and sea condition in today's forecast. Coastal waters in these areas are running moderate to rough, with wave heights of 1.2 to 2.8 meters — conditions that are dangerous for small watercraft.
Visayas
All provinces across the Visayas — Eastern Samar, Western Samar, Northern Samar, Leyte, Southern Leyte, Biliran, Cebu, Bohol, Negros Oriental, Negros Occidental, Iloilo, Capiz, Aklan, Antique, Guimaras, and the island province of Siquijor — fall under PAGASA's forecast for partly cloudy to cloudy skies with isolated rainshowers or thunderstorms driven by localized activity.
Coastal waters across the Visayas fall under the slight to moderate category, with wave heights of 0.6 to 1.8 meters. Winds are light to moderate, blowing from the southwest to west. While sea conditions are less severe than in Northern Luzon, fisherfolk and ferry passengers should remain cautious and check vessel advisories before departure.
Mindanao
Provinces across Mindanao — including Davao, Cotabato, Zamboanga, Bukidnon, Misamis Oriental, Misamis Occidental, Agusan del Norte, Agusan del Sur, Surigao del Norte, Surigao del Sur, Lanao del Norte, Lanao del Sur, and the provinces of the Bangsamoro Autonomous Region in Muslim Mindanao — are also expected to experience partly cloudy to cloudy skies with isolated rainshowers or thunderstorms from localized activity.
Winds in Mindanao are light to moderate, blowing from the south to southwest, with coastal waters in the slight to moderate range — wave heights of 0.6 to 1.8 meters. These are generally manageable conditions, though mariners should remain alert given the possibility of squalls associated with afternoon thunderstorms.
Decoding the Warnings: What the Hazards Mean for You
PAGASA has not raised any tropical cyclone wind signals or color-coded rainfall warnings in this forecast. However, the agency explicitly flags two hazards that apply nationwide wherever severe thunderstorms develop: flash floods and landslides.
A flash flood is a rapid, sudden rise in water level in low-lying areas, streets, riverbeds, and drainage channels — often occurring within minutes of a heavy downpour and with little warning. A landslide is the sudden movement of soil, rock, and debris down a slope, which can be triggered when heavy rain saturates the ground quickly. Both hazards do not require a named typhoon to occur; an intense but localized thunderstorm is enough to set them off.
If you live near a riverbank, an estero, a steep hillside, or a low-lying area prone to flooding, today's forecast warrants extra vigilance. Knowing how to interpret weather advisories before conditions worsen can save lives — learn how to read PAGASA's weather warnings so you are never caught off guard.
The most dangerous wind and sea conditions today are in Northern Luzon and the eastern sections of Central and Southern Luzon, where moderate to rough seas (waves up to 2.8 meters) have been forecast. PAGASA generally advises that rough sea conditions are hazardous to small vessels, and mariners in these areas should avoid venturing out unless absolutely necessary.
What It Means for You
Commuters
Expect traffic disruptions in Metro Manila and other urban centers if afternoon thunderstorms are intense. Streets in flood-prone areas can become impassable within minutes during a severe downpour. Leave earlier than usual, bring an umbrella or rain gear, and monitor local government announcements if rain intensifies during the morning or evening rush.
Fisherfolk and Small-Boat Operators
If you fish or operate small vessels off the coasts of Northern Luzon or the eastern sections of Central and Southern Luzon, today's conditions are the most hazardous in the country — waves reaching up to 2.8 meters and moderate to strong winds from the northeast to northwest. PAGASA strongly advises small-boat operators to stay ashore in these areas. Even in the Visayas and Mindanao, where seas are calmer, afternoon squalls associated with thunderstorms can develop quickly on the water.
Farmers
Isolated but potentially heavy thunderstorms across farming areas in Luzon, the Visayas, and Mindanao can bring both benefit and risk. Flash flooding in low-lying agricultural land and landslides in upland farms are hazards to watch for, particularly in the provinces of Palawan, Occidental Mindoro, and Oriental Mindoro where the habagat is most active. Secure equipment and harvest what is ready if your area is prone to flooding.
Students, Parents, and Schools
Classes scheduled for today should be monitored closely, as severe afternoon thunderstorms could prompt local government units to declare class suspensions. Parents should confirm whether schools have suspended face-to-face classes before sending children out, especially in provinces directly under the habagat's influence in Southern Luzon.
Outdoor Workers and Construction Sites
Workers in open-air environments — construction, agriculture, delivery services, and others — should plan for disruptions between the afternoon and early evening, when heat-driven localized thunderstorms are most likely to develop. Seek shelter at the first sign of thunder or lightning, and avoid open fields and tall structures during electrical storms.
Temperature Outlook
PAGASA's most recent temperature readings, recorded at its weather station in Science Garden, Diliman, Quezon City, showed a maximum of 33.0°C at 2:00 PM and a minimum of 25.0°C at 5:00 AM yesterday — reflecting the warm, humid conditions typical of the habagat season. Relative humidity peaked at 95% and dropped to a minimum of 58%, meaning it was oppressively muggy for much of the day.
Expect similar conditions today across Metro Manila, with heat and humidity combining to make the air feel hotter than the thermometer reads during midday hours — particularly before any afternoon thunderstorms bring temporary relief.
For reference, today's sunrise over Metro Manila is at 5:45 AM and sunset at 5:53 PM. High tide in Manila Bay is at 4:30 AM (1.03 meters), with a low tide at 2:37 PM (0.03 meters).
Bottom Line
The single most important thing you should do today: Check whether your home, route, or workplace sits in a flood-prone or landslide-prone area — and have a clear plan to move to higher or safer ground quickly if a severe thunderstorm strikes. Flash floods and landslides can develop with little warning even without a typhoon. If you are a fisherfolk or boater in Northern Luzon or eastern Central and Southern Luzon, stay ashore — seas are moderate to rough and winds are strong today.
Monitor official PAGASA updates at pagasa.dost.gov.ph.