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Nestled in the coastal state of Kerala in southern India, Thrissur occupies a strategic position in the cultural and geographic heartland of the region, often referred to as the 'cultural capital of Kerala.' The city lies approximately 50 kilometers inland from the Arabian Sea, situated at an average elevation of 2.9 meters above sea level, which places it within the low-lying coastal plains characteristic of this part of South Asia. Its terrain is predominantly flat, interspersed with gentle undulations and surrounded by the Western Ghats mountain range to the east, which significantly influences local weather patterns and air quality dynamics. Thrissur is enveloped by lush agricultural zones, primarily paddy fields and coconut groves, contributing to a distinct urban–rural gradient where the city center merges into peri-urban and rural landscapes. This setting means that while urban pollution sources like vehicle exhaust and construction dust are concentrated in the city, they can interact with agricultural residues and natural emissions from surrounding greenery. The proximity to the Arabian Sea moderates temperatures but also brings humid air that can trap pollutants, especially during calm wind conditions. The city's location away from major industrial belts, such as the Kochi industrial corridor to the south, means it lacks heavy industrial pollution, but localised emissions from gold jewellery workshops and festival activities become more pronounced in this relatively clean backdrop. The flat terrain and low elevation hinder pollutant dispersion, particularly during the dry months when atmospheric stagnation occurs, exacerbating air quality issues from road dust and waste burning.

Thrissur's air quality story unfolds across four distinct seasons, shaped by its tropical monsoon climate. From June to September, the southwest monsoon brings heavy rains that cleanse the air, washing away pollutants like road dust and reducing emissions from sources such as construction and waste burning; this period offers the best air quality, making it favourable for outdoor activities, though sensitive groups should be cautious of high humidity and potential mold spores. As the monsoon retreats in October and November, post-monsoon conditions see a gradual buildup of pollutants, with cooler temperatures and lower wind speeds starting to trap emissions. The peak pollution months from December to March coincide with the dry winter season, when temperature inversions are common in the early mornings, trapping vehicle exhaust, festival emissions from events like Thrissur Pooram (typically in April-May, but preparations and residual effects can extend into earlier months), and dust from construction and gold workshops; during these months, sensitive individuals such as those with respiratory conditions or the elderly should limit outdoor exposure, especially in the mornings when fog can mix with pollutants. From March to May, the pre-monsoon summer brings rising temperatures and occasional thunderstorms, which can temporarily clear the air but also stir up dust; wind patterns remain variable, often failing to disperse accumulated pollutants effectively. Throughout the year, the lack of strong prevailing winds, except during the monsoon, means that local emissions tend to linger, with health guidance emphasizing indoor air purification during peak months and leveraging the monsoon's cleansing effects for outdoor pursuits.