This study investigates the causes of the recent increase in the intensity and frequency of intense air pollution episodes in South Asia, particularly in Lahore, Pakistan. The "fifth season" refers to the recurring smog events that occur annually during the post-monsoon and winter periods, characterized by high concentrations of air pollutants, low visibility, and severe socio-economic disruptions. The study uses ground-based and satellite observations to analyze time-series data of PM2.5 and AOD, as well as satellite data on UVAAI, CO, and fire counts to determine fire incidences and aerosol characterization. The results indicate that the increase in air pollution is largely due to crop residue burning and motor vehicles, which contribute to the frequency and intensity of these events. Meteorological and topographical data analysis reveals that the Indo-Gangetic Plain (IGP) provides favorable conditions for the accumulation of pollutants, especially during the post-monsoon and winter periods. The study also highlights the role of transboundary pollution from agricultural fires in the region, emphasizing the need for regional cooperation to address this issue. The study concludes that the "fifth season" is a new climatic phenomenon in the IGP, and that transboundary pollution and regional cooperation are essential for mitigating the impact of air pollution on the region. The study also discusses the importance of air quality monitoring and the need for improved infrastructure to address the issue effectively.This study investigates the causes of the recent increase in the intensity and frequency of intense air pollution episodes in South Asia, particularly in Lahore, Pakistan. The "fifth season" refers to the recurring smog events that occur annually during the post-monsoon and winter periods, characterized by high concentrations of air pollutants, low visibility, and severe socio-economic disruptions. The study uses ground-based and satellite observations to analyze time-series data of PM2.5 and AOD, as well as satellite data on UVAAI, CO, and fire counts to determine fire incidences and aerosol characterization. The results indicate that the increase in air pollution is largely due to crop residue burning and motor vehicles, which contribute to the frequency and intensity of these events. Meteorological and topographical data analysis reveals that the Indo-Gangetic Plain (IGP) provides favorable conditions for the accumulation of pollutants, especially during the post-monsoon and winter periods. The study also highlights the role of transboundary pollution from agricultural fires in the region, emphasizing the need for regional cooperation to address this issue. The study concludes that the "fifth season" is a new climatic phenomenon in the IGP, and that transboundary pollution and regional cooperation are essential for mitigating the impact of air pollution on the region. The study also discusses the importance of air quality monitoring and the need for improved infrastructure to address the issue effectively.