<p>This study evaluates the seasonal variability of the Air Quality Index (AQI) across four ambient air quality monitoring sites in the Bilaspur district of Chhattisgarh, India, Bilaspur City (AS1), Masturi (AS2), Takhatpur (AS3), and Sipat (AS4), during the premonsoon, monsoon, and postmonsoon seasons of 2021. Eight major air pollutants (PM₁₀, PM_2.5, NOₓ, SO₂, CO, O₃, NH₃, and Pb) were analyzed to assess spatiotemporal patterns in regional air quality. The results identified PM₁₀ and PM_2.5 as the dominant contributors to AQI deterioration, particularly during the premonsoon and postmonsoon periods, with AQI values ranging from 86.0 to 240.7, classifying most locations under moderate to poor air quality. In contrast, monsoon rainfall significantly lowered particulate concentrations, resulting in predominantly satisfactory AQI levels. One-way ANOVA followed by Tukey’s HSD test showed no detectable seasonal differences among the sites (<i>p</i> &gt; 0.05; F = 0.47 to 0.62), indicating uniform pollutant dispersion across the study area. The analysis was confined to 2021 due to the availability of complete, quality-assured datasets representing a stable post-lockdown baseline, ensuring consistency and minimizing data gaps. The annual AQI for 2021 reflects moderate pollution levels, underscoring the need for sustained monitoring and targeted emission control strategies in rapidly urbanizing regions of central India.</p> Graphical Abstract <p></p>