The Indian subcontinent has some of the highest annual average ambient Particulate Matter (PM) exposure levels in the world, but there is limited monitoring, both in terms of scope and scale. Most of the effort towards air pollution monitoring and assessment is focused on cities with populations greater than one million. But 230 million people, more than half of India’s urban population, live in towns and cities with a population of less than one million. This study examines the impact on air quality due to the reduction in anthropogenic activity during the Covid lockdown in three small cities in northern India: Bulandshahr, Sonipat and Patiala, all with populations less than half a million. Data from Delhi has also been used to visually illustrate the impact of the lockdown in a large city in the same climate zone as the study cities, and where lockdown restrictions were stringently enforced. For this study, air quality data from January 2018 through September 2023 was collected from government monitoring stations, and some pre- and post-Covid data from low-cost monitors deployed by the authors. Statistical analyses—descriptive (mean, SD, and percentiles), inferential (two t-tests) and ANOVA—were done for data from November 2019 to February 2021 to assess the variation in air quality for the pre-, during and post-Covid periods. (The remainder of the data from 2018 to 2023 has been used for visual comparisons.) The findings show that while there is a dramatic improvement in the air quality of the study cities during the Covid lockdown, the post-Covid lockdown air quality worsened rapidly and returned to pre-Covid levels in less than a year. Findings indicate that air quality is strongly correlated with anthropogenic activities and so one can conclude that air quality can be regulated by regulating human activities. The findings of the study will help in framing state and regional level policies for addressing poor air quality in non-metro urban areas and achieving the sustainable development goals (SDGs) linked to public health, reduction in the adverse environmental impact of cities, and adaptation to climate change, as indicated by SDGs 3.9, 11.6 and 11.b.