Outside the usual range27 September 2026Environment
Tamil Nadu: average air quality index over the 7 days to 27 September 2026 was 87, above the 5-year median of 47 for the same week (+84%).
What happened
- 7-day mean to 27 September 2026
- 87
- That day alone: 106
- 5-year median, same week
- 47
- Change
- +40
- Change, per cent
- +84%
Why it matters
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 average air quality index, lower is better. This movement is therefore assessed as a deterioration.
Historical context
The number being averaged changed (about 2 now against 8 in earlier years), so part of this reflects which places are measured. Same week in earlier years: 2025 47, 2024 47, 2023 44, 2022 68, 2021 62. Daily values are compared as 7-day means because a single day mostly reflects weather.
The underlying data
| Period | Value | Release | Where in the document |
|---|---|---|---|
| 27 September 2026 | 106 | CPCB National Air Quality Index bulletin, 27 September 2026 (235 cities) | AQI bulletin p.3–11, Index Value column: mean of 3 city rows placed in Tamil Nadu — Chennai (p.3), Gummidipoondi (p.5), Thoothukudi (p.11) |
| 26 September 2026 | 95 | CPCB National Air Quality Index bulletin, 26 September 2026 (243 cities) | AQI bulletin p.3–12, Index Value column: mean of 3 city rows placed in Tamil Nadu — Chennai (p.3), Gummidipoondi (p.5), Thoothukudi (p.12) |
| 25 September 2026 | 91 | CPCB National Air Quality Index bulletin, 25 September 2026 (244 cities) | AQI bulletin p.3–12, Index Value column: mean of 3 city rows placed in Tamil Nadu — Chennai (p.3), Gummidipoondi (p.5), Thoothukudi (p.12) |
| 24 September 2026 | 116 | CPCB National Air Quality Index bulletin, 24 September 2026 (245 cities) | AQI bulletin p.4–12, Index Value column: mean of 3 city rows placed in Tamil Nadu — Chennai (p.4), Gummidipoondi (p.5), Thoothukudi (p.12) |
| 23 September 2026 | 83 | CPCB National Air Quality Index bulletin, 23 September 2026 (239 cities) | AQI bulletin p.4, Index Value column: mean of 1 city row placed in Tamil Nadu — Chennai (p.4) |
Source and method
- Release
- CPCB National Air Quality Index bulletin, 27 September 2026 (235 cities)Archived fileOriginal URLFirst seen 3 Oct 2026
More signals for average air quality index in Tamil Nadu
- Tamil Nadu: average air quality index of 54 on 22 September 2026 is the lowest since 22 June 2026.
- Tamil Nadu: average air quality index of 168 on 17 September 2026 is the highest since 31 December 2025.
- Tamil Nadu: average air quality index of 155 on 5 September 2026 is the highest since 31 December 2025.
- Tamil Nadu: average air quality index over the 7 days to 2 September 2026 was 81, above the 5-year median of 48 for the same week (+68%).
Cite this
According to the India Health Observatory, Tamil Nadu: average air quality index over the 7 days to 27 September 2026 was 87, above the 5-year median of 47 for the same week (+84%). Source: Central Pollution Control Board, Ministry of Environment, Forest and Climate Change, CPCB National Air Quality Index bulletin, 27 September 2026 (235 cities). https://indiahealthobservatory.com/signals/air-quality-index--tamil-nadu--2026-09-27--baseline_breach
See also Tamil Nadu and 106 AQI in context.