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Sigma, a coastal municipality in the province of Capiz, Philippines, occupies a relatively flat terrain along the northern coast of Panay Island. Situated at 11.4214°N, 122.6662°E, its geography is profoundly shaped by its proximity to the Sibuyan Sea. The town’s landscape is a mosaic of agricultural lands – primarily rice paddies and coconut plantations – interspersed with residential areas and a growing commercial center. The urban-rural gradient is quite pronounced; the *poblacion* (town center) is densely populated, while the surrounding barangays are largely agricultural. This creates localized variations in air quality. The surrounding landscape features low-lying hills inland, but the immediate coastal area is dominated by mangrove forests and beaches. While Sigma isn’t a major industrial hub, regional agricultural practices, including the burning of agricultural waste after harvest, contribute to particulate matter. The prevailing winds, generally from the southeast during the wet season and northeast during the dry season, play a crucial role in dispersing or concentrating pollutants. The open coastal location means pollutants can be readily transported offshore, but also potentially drawn in from neighboring areas. The lack of significant topographical barriers allows for relatively good ventilation, but localized conditions can still lead to pollutant build-up.

Sigma experiences a distinct wet and dry season, heavily influenced by the southwest monsoon (habagat) and the northeast monsoon (amihan). Air quality generally improves during the wet season (roughly June to November) due to increased rainfall which effectively washes away particulate matter and suppresses dust. However, increased humidity can also promote the formation of mold and allergens. The dry season (December to May) typically sees a decline in air quality. Agricultural burning, common after the rice harvest in February and March, significantly elevates particulate matter levels. This period, coupled with lower wind speeds, creates conditions for pollutant accumulation. Temperature inversions, though less frequent than in larger cities, can occur during calm mornings in the dry season, trapping pollutants near the ground. March and April are generally the least favourable months for outdoor activity for those with respiratory sensitivities. November and December, with the onset of the amihan, offer the best air quality. Sensitive groups – children, the elderly, and those with pre-existing respiratory conditions – should limit strenuous outdoor activity during peak dry season months and consider using masks when agricultural burning is prevalent. Monitoring wind direction can help predict pollutant transport.