Delhi’s average Air Quality Index for September was 102, the lowest September figure in the five-year series published by the Union environment ministry on September 30. The corresponding averages were 105 in both 2025 and 2024, 108 in 2023 and 104 in 2022. A better monthly average does not mean every day had clean air.
A separate Centre for Science and Environment assessment released that day examined June 1 to August 31. Of those 92 days, one was in the Good category, 35 were Satisfactory, 53 Moderate and three Poor. CSE called for sustained emissions reductions across the National Capital Region.
These different periods and measures are not contradictory. CSE’s rainfall analysis also does not isolate rain from other weather conditions or changes in emissions.