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San Juan del Sur, nestled on Nicaragua’s Pacific coast within the Rivas department, presents a fascinating interplay between coastal geography and developing urbanisation. The city itself is built on a peninsula, flanked by the Pacific Ocean on one side and a series of hills and valleys on the other, creating a microclimate influenced by both marine and terrestrial factors. Elevation rises quickly inland, transitioning from the beachside town to more rugged, forested terrain. This topography significantly impacts air quality; the hills can trap pollutants, particularly during calm weather conditions, while the ocean provides a degree of dispersion. The surrounding landscape is a mix of agricultural land – primarily subsistence farming and some cattle ranching – and increasingly, tourism-related development. While San Juan del Sur doesn’t have heavy industry, the growing number of construction projects, coupled with the dust from unpaved roads, contribute to particulate matter. The urban-rural gradient is sharp; immediately outside the town, the landscape quickly becomes rural, but increased vehicle traffic and wood-burning stoves in peri-urban areas still impact localised air quality. The city’s position within a tropical climate means humidity is consistently high, influencing pollutant behaviour and dispersion.

San Juan del Sur experiences a pronounced wet and dry season, dictating the patterns of air quality. The dry season, typically from December to April, sees the lowest rainfall and strongest winds, which generally offer good dispersion of pollutants. However, this period also coincides with increased dust from agricultural activities and construction, and a higher reliance on burning for land clearing, leading to elevated particulate matter. February and March are often the dustiest months. The transition months of May and November can be unpredictable, with intermittent rainfall and shifting wind patterns. The wet season, from May to November, brings frequent rainfall which effectively washes pollutants from the air, resulting in generally improved air quality. However, increased humidity can promote mould growth, impacting respiratory health. September and October, peak months for rainfall, usually offer the cleanest air. During the wet season, stagnant air can occur between rain events, trapping localised pollutants. Sensitive groups – children, the elderly, and those with respiratory conditions – should be particularly cautious during the dry season and periods of stagnant air, limiting strenuous outdoor activity and considering the use of masks when dust levels are high.