As Habagat lingers, farms and food supplies face growing risks

Heavy flooding across Central Luzon and Metro Manila in late August 2026 showed how monsoon variability has become more destructive. Rainfall totals exceeded 300 to 400 millimeters in just three days, a volume that historically would have been spread across a month. The Pampanga and Pasig rivers overflowed, while urban drainage systems were overwhelmed by the concentrated rainfall. The event was the result of several interacting drivers: atmospheric dynamics, ocean warming, topographic amplification, climate change and ecological degradation. Together, these factors have contributed to the persistence of Habagat into the Ber months, disrupting what was once considered a predictable seasonal transition. The Ber months — September to December — traditionally signaled the onset of Amihan, bringing cooler, drier conditions favorable for harvest and post-harvest activities. Recent climate variability, amplified by La Niña and warming seas, has prolonged Habagat rains into September and October, disrupting cropping calendars, post-harvest drying and flood management. Article continues after this advertisement The expectation that the Ber months mean Amihan has weakened amid climate variability and ecological disruption. Extended Habagat seasons are reshaping the agricultural and disaster risk landscapes of Luzon. Scientific evidence cited in this report points to atmospheric interactions, ocean warming, ENSO variability and ecological degradation as drivers of this shift. Together, they intensify rainfall, delay the onset of cooler winds and increase flood risks across rice-producing areas and urban centers. When the seasons stop following the calendar The Philippines, an archipelagic nation in the western Pacific, has long been defined by its monsoon cycles. The southwest monsoon, locally known as Habagat, traditionally dominates from June to September, bringing heavy rains that sustain rice cultivation and replenish water systems. The northeast monsoon, Amihan, ushers in cooler, drier air from Siberia beginning in late September, marking the start of the so-called Ber months. This seasonal rhythm historically provided a reliable framework for agricultural planning, disaster preparedness and cultural expectations. Farmers aligned their cropping calendars with the anticipated arrival of Amihan, while communities prepared for reduced flood risks and cooler weather. In recent decades, however, Habagat rains have persisted well into September and October, undermining traditional expectations and exposing systemic vulnerabilities. Historically, the monsoon transition was considered predictable. Pagasa records from the 1960s through the 1980s show that Amihan typically arrived by mid-September, stabilizing weather conditions and enabling rice harvests in Central and Northern Luzon (David, 2009). Article continues after this advertisement This predictability allowed farmers to rely on sun-drying methods for post-harvest processing, helping ensure that grain moisture levels met IRRI standards. Flood risks also declined by late September, allowing government agencies to shift their focus from relief operations to storage and distribution. By the 1990s, however, anomalies had begun to emerge. The 1995 La Niña event delayed the onset of Amihan by nearly a month, causing widespread flooding in Central Luzon and disrupting rice harvests. Similar disruptions occurred in 2011 and 2020, when extended Habagat rains led to crop losses exceeding 200,000 metric tons (FAO, 2021). Article continues after this advertisement The persistence of Habagat into the Ber months is driven by multiple scientific factors. Atmospheric interactions between cooler Amihan winds and moisture-laden Habagat flows intensify rainfall rather than suppress it. Oceanic drivers, particularly warmer sea surface temperatures in the West Philippine Sea, now about 1.5 degrees Celsius above historical averages, increase evaporation and moisture transport. Topographic amplification further magnifies rainfall as mountain ranges such as the Sierra Madre and Cordilleras force moist air upward, releasing torrential rain over Luzon’s plains. Climate change and ENSO variability add another layer of disruption, delaying Amihan’s onset by two to three weeks compared with the 1980s. Deforestation and watershed degradation exacerbate these effects by reducing the capacity of mountain ecosystems to absorb runoff and help prevent landslides. The consequences for agriculture are significant. Rice, the Philippines’ staple crop, is highly sensitive to rainfall variability. Extended Habagat seasons increase the risks of lodging, waterlogging and spoilage, while post-harvest drying becomes unreliable because of persistent cloud cover and rainfall. Grain moisture levels often exceed IRRI’s recommended 14%, undermining storage stability and food quality (IRRI, 2018). Vegetable crops, particularly those grown in Central Luzon, suffer from waterlogging and rot, reducing supply and increasing market volatility. Disaster preparedness is also strained. Flood risks in NCR, Central Luzon and Northern Luzon remain elevated well into October, putting pressure on urban drainage systems and buffer stock logistics. The late August 2026 floods, which brought more than 300 millimeters of rainfall in three days, illustrate this systemic challenge. This report builds on the study “Habagat and Amihan Variability Affects Food Systems and Disaster Risk Management,” extending its analysis through historical background, scientific explanations and scenario modeling. By placing current variability within a broader historical and scientific context, the report underscores the need for adaptive agricultural planning, strengthened disaster preparedness and cooperative governance reforms. The persistence of Habagat into the Ber months is not merely a meteorological anomaly but a systemic challenge requiring action. Without adaptation, the Philippines risks chronic food insecurity, escalating disaster vulnerability and weakened resilience in the face of climate change. Why Habagat is lasting longer August floods signal a changing monsoon The heavy flooding across Central Luzon and Metro Manila in late August 2026 illustrated the destructive effects of monsoon variability. Rainfall totals exceeded 300 to 400 millimeters in just three days, compared with a volume that historically would have been spread across a month. The Pampanga and Pasig rivers overflowed, while urban drainage systems were overwhelmed by the concentrated rainfall. The flooding reflected the interaction of atmospheric dynamics, ocean warming, topographic amplification, climate change and ecological degradation. These factors contribute to the persistence of Habagat into the Ber months, turning what was once regarded as a predictable seasonal transition into a prolonged overlap between monsoon systems. When Habagat and Amihan collide The transition between Habagat and Amihan is not a clean handover but an overlapping period. During the intermonsoon period, Amihan’s cooler, denser air masses from Siberia collide with Habagat’s warm, moisture-rich flows from the southwest. Instead of suppressing rainfall, this interaction enhances vertical lifting. Cooler Amihan winds act as a wedge, forcing Habagat air upward, where it cools and condenses into heavy rain. Studies on monsoon dynamics (Webster & Fasullo, 2003; Wang et al., 2017) show that overlapping monsoon systems often intensify precipitation through thermodynamic instability. The Philippines, situated at the boundary of tropical and subtropical circulation, experiences this overlap acutely. Radiosonde data from PAGASA show that vertical wind shear increases during September, enhancing convective instability. This helps explain why rainfall peaks during the supposed transition period. The Intertropical Convergence Zone, or ITCZ, also shifts northward during late August and September, aligning with Habagat flows. When Amihan begins to intrude, the ITCZ does not retreat immediately, creating a dual convergence zone. This overlap sustains rainfall even as cooler winds arrive. The August 2026 floods illustrate this interaction: Amihan winds forced Habagat’s moisture upward, producing rainfall intensities of 100 to 150 millimeters a day. Atmospheric interactions can therefore turn an expected decline in rainfall into an intensification. The Ber months are no longer consistently associated with dry breezes as overlapping atmospheric dynamics prolong Habagat conditions. Warmer seas, heavier rains Sea surface temperatures, or SSTs, in the West Philippine Sea and South China Sea are about 1.5 degrees Celsius above the 1970s baseline. According to the Clausius-Clapeyron relation, warmer air holds about 7% more water vapor for every 1 degree Celsius of warming. At 1.5 degrees Celsius, this translates to about 10% to 11% more atmospheric moisture capacity. Trenberth et al. (2014) emphasize that ocean warming intensifies monsoon systems by increasing the amount of moisture available to winds. Satellite data from NOAA show that August 2026 SST anomalies reached 1.3 to 1.5 degrees Celsius, increasing evaporation rates. Even weakened Habagat flows carried 20% to 30% more water vapor than historical averages. This helps explain why rainfall remained intense despite the gradual arrival of Amihan. Ocean warming also interacts with ENSO variability. During La Niña, cooler equatorial Pacific waters strengthen the Walker circulation, enhancing moisture transport into the West Philippine Sea. This combination of regional warming and ENSO-driven circulation creates what the report describes as a “supercharged Habagat.” During the August floods, moisture flows into Luzon were 25% higher than the 1981-2010 climatology. Oceanic drivers therefore contribute to heavier, longer-lasting and more destructive Habagat rains. Warmer seas provide additional atmospheric moisture, allowing even weakened winds to deliver torrential rainfall. How Luzon’s mountains intensify rainfall The Philippines’ rugged terrain magnifies rainfall through orographic lifting. Moist Habagat winds encounter mountain ranges such as the Zambales, Sierra Madre and Cordilleras. As air rises, it cools adiabatically and condenses into rain. Chang et al. (2005) demonstrated that orographic effects can double rainfall intensity in monsoon regions. In late August 2026, Doppler radar data showed rainfall maxima along the slopes of the Sierra Madre, where uplift was strongest. Central Luzon’s plains, lying leeward of these ranges, became flood basins. The Cordilleras amplified rainfall in northern provinces, triggering landslides in Benguet and Ifugao. Urban areas such as Metro Manila are particularly vulnerable because runoff from upland areas converges in lowland drainage systems. During the August floods, rainfall totals in upland Bulacan exceeded 350 millimeters, with runoff flowing into the Marilao and Meycauayan rivers. Topography therefore transforms atmospheric moisture into localized flood hazards. The persistence of Habagat into September means prolonged exposure to orographic amplification, compounding risks for Luzon’s rice-producing areas and urban centers. Climate change and La Niña stretch the wet season Climate change has delayed Amihan’s onset by two to three weeks compared with the 1980s. Historical PAGASA records show that Amihan winds typically arrived by mid-September; onset now occurs in October. This delay is linked to jet stream waviness and Arctic amplification, which slow atmospheric circulation (Francis & Vavrus, 2012). ENSO variability further complicates monsoon transitions. La Niña conditions in 2026 strengthened Habagat flows, sustaining rainfall into October. McPhaden et al. (2006) note that La Niña enhances convection in the western Pacific, prolonging wet seasons. Climate models project that at 2 degrees Celsius of global warming, atmospheric moisture capacity will increase by about 14%, making extreme Habagat events more frequent. The August floods indicate the risks posed by concentrated rainfall events. Climate change and ENSO effects therefore delay Amihan, prolong Habagat and intensify rainfall. Reliance on historical seasonal calendars is becoming increasingly untenable. Lost forests, greater flood risk Deforestation reduces the capacity of mountains to buffer runoff. Forests regulate hydrology through evapotranspiration and root stabilization. Lasco & Pulhin (2006) emphasize that forest loss accelerates flooding and landslides. In August 2026, denuded slopes in Nueva Ecija and Bulacan amplified runoff, overwhelming rivers. Landslides in the Sierra Madre foothills were linked to logging and quarrying. Without forest cover, rainfall that might otherwise have been absorbed flowed into lowlands. Watershed degradation also undermines aquifer recharge, reducing resilience during prolonged wet seasons. Urban sprawl in Pampanga and Bulacan has converted floodplains into impermeable surfaces, further accelerating runoff. Ecological degradation therefore magnifies the effects of monsoon variability. Extended Habagat seasons become more damaging not only because of atmospheric and oceanic drivers but also because landscapes have lost some of their natural defenses. Three scenarios for a longer wet season The persistence of Habagat into the Ber months creates distinct scenarios with varying agricultural and disaster impacts: Delayed Amihan, with an October arrival: Moderate flood risk, unreliable sun-drying, higher costs because of the need for mechanical dryers and extended pressure on urban drainage systems. Extended Habagat, with September-October dominance: Significant rice losses from lodging and flooding, grain moisture exceeding IRRI standards, compromised storage and high flood risk across Luzon. Supercharged Habagat, with La Niña and warm seas: Severe crop losses, essential use of mechanical drying, overwhelmed storage facilities and extreme flood events requiring prolonged relief operations. These scenarios underscore the systemic risks of relying on historical seasonal patterns amid a changing climate. A new monsoon reality The expectation that the Ber months mean Amihan has weakened under climate variability and ecological disruption. Extended Habagat seasons now persist into September and October, reshaping the agricultural and disaster risk landscapes of Luzon. The late August 2026 floods demonstrate that monsoon transitions are becoming less predictable and more prolonged. Scientific evidence cited in this report points to atmospheric interactions, ocean warming, ENSO variability and ecological degradation as the primary drivers of this shift. These factors converge to intensify rainfall, delay the onset of cooler winds and increase flood risks across rice-producing areas and urban centers. Rice harvests are increasingly vulnerable to lodging, waterlogging and spoilage, while post-harvest drying faces persistent disruption because of unreliable sun exposure. Grain moisture levels often exceed standards, undermining food quality and storage stability. Disaster preparedness is similarly strained as flood risks extend into months traditionally considered safer, putting pressure on drainage systems and buffer stock logistics. The persistence of Habagat into the Ber months is not merely a meteorological anomaly but a systemic challenge requiring adaptive agricultural planning, strengthened disaster preparedness and cooperative governance reforms. Without decisive action, the Philippines risks chronic food insecurity and escalating disaster vulnerability. Adapting to a longer, wetter Habagat Rethinking the farm calendar Recalibrate cropping calendars using downscaled climate forecasts and seasonal outlooks from PAGASA and IRRI. Farmers should adopt flexible planting schedules aligned with rainfall variability rather than fixed monsoon dates. Invest in mechanical dryers and flood-resilient storage facilities to reduce dependence on sun-drying. Cooperative-owned dryers can lower costs and ensure equitable access. Storage facilities should be elevated, ventilated and moisture-controlled to protect grain quality. Promote diversified cropping systems by integrating root crops such as cassava, sweet potato, gabi and ube, as well as legumes and flood-resilient perennial vegetables. Diversification reduces risk exposure and stabilizes farmer incomes during prolonged wet seasons. Preparing for a longer flood season Extend flood monitoring and relief readiness, with LGUs maintaining contingency plans for prolonged rainfall. Early warning systems should integrate satellite rainfall data and community-based alerts. Strengthen urban drainage and upland reforestation to buffer runoff. Investments in green infrastructure, including trees and retention ponds, can complement traditional drainage systems. Reforestation of the Sierra Madre and Zambales ranges can help restore natural flood regulation. Expand buffer stock facilities by regionalizing storage hubs in Luzon, the Visayas and Mindanao. Stocks should be climate-controlled and strategically located to ensure rapid deployment during prolonged wet seasons. Making climate planning a shared responsibility Integrate climate forecasts into farmer cooperatives so planting and harvesting decisions are coordinated at scale. Cooperative scheduling reduces individual risk and enhances collective bargaining. Negotiate better terms for post-harvest services through federated farmer groups. Collective contracts for dryers, storage and logistics can reduce costs and improve resilience. Your subscription could not be saved. Please try again. Your subscription has been successful. Institutionalize scenario modeling in national food security planning by incorporating rainfall outcome tables into NFA and DA strategies. This would ensure that fiscal allocations, buffer stock releases and import contracts are climate-responsive rather than historically fixed. /dm