Air pollution over the megacity New Delhi has gained significant attention in recent times. Local pollution, along with advection from upwind sources, long-range transport and festivities (e.g., Diwali) contributing large emissions from firecrackers, has led to high loading conditions over the city. In this study, we assess a particulate pollutant event that coincided with the festival of Diwali in 2016 using multiple parameters related to particulate pollution from the ground and satellite based measurements in relation to the observed climatology during the period of 2000 to 2016. Our analysis reveals that the episode of severe air pollution in 2016 was exacerbated by the long-range transport of absorbing fine aerosols emanating from biomass/stubble burning in the adjacent states to the northwest of National Capital Territory (NCT) of India. Based on concentration weighted trajectory (CWT) analysis using the PM2.5 mass concentration and AOD, the high loading conditions were related to trajectories that passed through the northwest of NCT. The period after Diwali in 2016 also coincided with air masses traversing large biomass burning areas. The long-term changes in the fire counts indicate that these events have been increasing at an alarming rate of ~25% per year since 2000, creating the potential for high particulate pollution over downwind cities such as Delhi.