Tamil Nadu: share of cities with poor air over the 7 days to 10 September 2026 was 6%, above the 5-year median of 0% for the same week (+5.7 points).

Daily figures mostly reflect the weather, so the observatory compares the mean of the last seven days with the same week in up to five earlier years. A breach means this week sits well outside what those years would lead you to expect, and by at least 15%. It is reported when an unusual run begins and for the latest day while it lasts, not every day.

For share of cities with poor air, lower is better. This movement is therefore assessed as a deterioration.

The number being averaged changed (about 5 now against 9 in earlier years), so part of this reflects which places are measured. Same week in earlier years: 2025 1%, 2024 0%, 2023 6%, 2022 0%, 2021 0%. Daily values are compared as 7-day means because a single day mostly reflects weather.

Full history of share of cities with poor air in Tamil Nadu