Sylhet Air Quality Index (AQI)

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Nestled in northeastern Bangladesh's Surma Valley, Sylhet occupies a distinctive geographic position that profoundly shapes its urban character and air quality patterns. Situated at approximately 24.9°N latitude and 91.9°E longitude, this city of nearly half a million residents lies within the Sylhet Basin, surrounded by the Khasi and Jaintia Hills to the north and east, which create a natural amphitheater effect. The terrain slopes gently from these hills toward the floodplains of the Surma and Kushiyara rivers, with the city itself at an elevation of about 35 meters above sea level. This basin configuration, combined with proximity to the Meghalaya plateau, creates a semi-enclosed environment where pollutants can accumulate, particularly during periods of atmospheric stability. Sylhet's urban-rural gradient is pronounced, transitioning rapidly from dense commercial centers to tea gardens and agricultural zones within the metropolitan region. The city serves as the economic hub for Bangladesh's northeastern tea-producing districts, with surrounding areas dominated by rice paddies, tea plantations, and natural wetlands. While not part of Bangladesh's major industrial belt, Sylhet experiences pollution from general urban sources including vehicular emissions, construction dust, brick kilns operating in peri-urban areas, and biomass burning for domestic cooking. The Surma River flowing through the city provides some ventilation but also contributes to humidity that can interact with pollutants. This unique combination of basin topography, agricultural surroundings, and growing urban development creates complex air quality dynamics specific to Sylhet's geographic context.

Sylhet's air quality follows a distinct seasonal rhythm shaped by the South Asian monsoon system and local meteorological patterns. During winter (December-February), cool temperatures and frequent temperature inversions trap pollutants close to the ground, creating persistent haze that often peaks in January. The city's basin location exacerbates this effect, with calm winds allowing particulate matter from urban sources and agricultural residue burning to accumulate. Sensitive groups should limit outdoor activities during morning hours when inversions are strongest. Spring (March-May) brings gradually rising temperatures and pre-monsoon thunderstorms that provide some cleansing through rainfall, though dust from dry agricultural fields can temporarily worsen air quality. The summer monsoon (June-September) offers the cleanest air as heavy rainfall from the Bay of Bengal branch of the monsoon effectively scrubs pollutants from the atmosphere, with July typically showing the best conditions for outdoor activities. However, high humidity can make existing pollutants feel more oppressive. Autumn (October-November) marks the transition period as monsoon rains retreat, allowing pollution to gradually build up again, particularly from post-harvest agricultural burning in surrounding areas. Throughout the year, fog is common during cooler months and can combine with pollutants to create dense smog. The city's proximity to hills influences local wind patterns, with valley breezes sometimes providing ventilation but also potentially transporting pollutants from surrounding areas into the urban basin.