SmogRank / India / Tamil Nadu / Chennai
Chennai, month by month
Chennai has a measured daily mean on 1,072 days since 7 May 2023. Its worst month was January 2025, at 155 US AQI (61.6 µg/m³), 21st of 2,474 cities on that month's world ranking. Its cleanest was April 2026, at 63 US AQI (15.7 µg/m³). 2025 averaged 94 US AQI (32.3 µg/m³), against 94 US AQI (32.0 µg/m³) in 2024.
Every month since 2023
The US EPA's Air Quality Index for PM2.5 (2024 breakpoints). Show values as: µg/m³ · US AQI · India AQI · China AQI · European AQI · UK DAQI · Canada AQHI+. About the scales
Months without a mean, and why
7 months
| Month | Why |
|---|---|
| Jan 2026 | 21 of 31 days measured; a month needs 22. The others: 10 with under 18 hours of readings or readings that failed our checks. |
| Jul 2024 | 2 of 31 days measured; a month needs 22. The others: 29 with under 18 hours of readings or readings that failed our checks. |
| Jun 2024 | No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks. |
| May 2024 | 17 of 31 days measured; a month needs 22. The others: 14 with under 18 hours of readings or readings that failed our checks. |
| Dec 2023 | 19 of 31 days measured; a month needs 22. The others: 12 with under 18 hours of readings or readings that failed our checks. |
| Nov 2023 | No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks. |
| Oct 2023 | No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks. |
A day counts once 18 hours of it are measured; a month needs 70% of its days.
Chennai's worst months
| Month | US AQI | World rank |
|---|---|---|
| January 2025 | 15561.6 µg/m³ | 21stof 2,474 |
| December 2025 | 14252.1 µg/m³ | 188thof 3,006 |
| January 2024 | 14151.8 µg/m³ | 31stof 2,385 |
| November 2024 | 14051.3 µg/m³ | 28thof 2,624 |
| February 2026 | 13448.9 µg/m³ | 111thof 2,866 |
| December 2024 | 11842.6 µg/m³ | 35thof 2,616 |
Monthly means over the days measured; finished months only. World rank: its place on that month's world ranking of every city with enough days. Each month opens that ranking.
Chennai's worst days
| Day | US AQI |
|---|---|
| 31 Oct 2024 | 259184.0 µg/m³ |
| 14 Jan 2024 | 238163.0 µg/m³ |
| 20 Oct 2025 | 191112.0 µg/m³ |
| 13 Jan 2024 | 188108.0 µg/m³ |
| 30 Oct 2024 | 18299.8 µg/m³ |
| 22 Dec 2023 | 18197.7 µg/m³ |
| 20 Dec 2025 | 17793.3 µg/m³ |
| 21 Dec 2023 | 17792.4 µg/m³ |
| 1 Jan 2024 | 17791.9 µg/m³ |
| 21 Dec 2025 | 17690.8 µg/m³ |
Daily means, the highest since 7 May 2023; the WHO's daily guideline is 15 µg/m³. Each date opens that day's world ranking, and each episode the bad-air spell it was part of.
Use this history
SmogRank, PM2.5 monthly and daily means, Chennai, India, 7 May 2023 – 11 Oct 2026. Monitor data from CPCB and AirNow, via OpenAQ and from the publisher directly; sources listed at smogrank.com/sources. smogrank.com/in/chennai/history (accessed 12 Oct 2026).
You're welcome to reuse a single chart, image or figure with this citation and a link. Terms. Raw monitor readings in bulk are published by OpenAQ, under each provider's licence.
Chennai now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-12 23:07 UTC. Values are PM2.5 (fine particles), the median of each city's monitors, as the US AQI PM2.5 sub-index. Some low-cost readings: Sensor.Community, ODbL (data and licence). Some readings: Uzhydromet (Uzbekistan's Hydrometeorological Service); Department of Environment, Nepal; Vietnam's government monitors; Aurassure; Umhverfisstofnun (Environment Agency of Iceland); RMCAB (Secretaría Distrital de Ambiente, Bogotá); Love My Air (City and County of Denver), no reuse terms published (why we use them).