Tamil Nadu: highest city air quality index over the 7 days to 3 October 2026 was 179, above the 5-year median of 82 for the same week (+117%).

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 highest city air quality index, lower is better. This movement is therefore assessed as a deterioration.

This continues an unusual run that began earlier. Same week in earlier years: 2025 137, 2024 82, 2023 76, 2022 208, 2021 75. Daily values are compared as 7-day means because a single day mostly reflects weather.

Full history of highest city air quality index in Tamil Nadu