SmogRank / United States / Alabama / Decatur
Decatur, month by month
Decatur has a measured daily mean on 1,250 days since 1 January 2023. Its worst month was June 2023, at 55 US AQI (11.3 µg/m³), 611th of 1,603 cities on that month's world ranking. Its cleanest was October 2025, at 28 US AQI (5.0 µg/m³). 2025 averaged 39 US AQI (7.0 µg/m³), against 42 US AQI (7.5 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
3 months
| Month | Why |
|---|---|
| Apr 2023 | 5 of 30 days measured; a month needs 21. The others: 3 missing from OpenAQ's archive, 22 with under 18 hours of readings or readings that failed our checks. |
| Mar 2023 | 6 of 31 days measured; a month needs 22. The others: 20 missing from OpenAQ's archive, 5 with under 18 hours of readings or readings that failed our checks. |
| Feb 2023 | 2 of 28 days measured; a month needs 20. The others: 25 missing from OpenAQ's archive, 1 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.
Decatur's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| June 2023 | 5511.3 µg/m³ | 611thof 1,603 | – |
| February 2026 | 5511.3 µg/m³ | 1,131stof 2,866 | – |
| August 2024 | 5410.6 µg/m³ | 510thof 2,010 | – |
| March 2026 | 5310.0 µg/m³ | 1,675thof 2,971 | South-eastern United States, March 2026 |
| May 2023 | 519.1 µg/m³ | 629thof 1,600 | – |
| July 2023 | 509.0 µg/m³ | 763rdof 1,432 | – |
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.
Decatur's worst days
| Day | US AQI | Episode |
|---|---|---|
| 9 Feb 2026 | 14151.6 µg/m³ | – |
| 19 Mar 2026 | 8326.5 µg/m³ | South-eastern United States, March 2026 |
| 2 Aug 2024 | 8024.7 µg/m³ | – |
| 1 Aug 2024 | 8024.5 µg/m³ | – |
| 21 Feb 2024 | 8024.4 µg/m³ | – |
| 22 Mar 2023 | 7723.1 µg/m³ | – |
| 30 Jun 2023 | 7521.9 µg/m³ | – |
| 14 Feb 2026 | 7220.6 µg/m³ | – |
| 8 Jun 2023 | 7220.4 µg/m³ | – |
| 15 Aug 2026 | 7119.9 µg/m³ | – |
Daily means, the highest since 1 Jan 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, Decatur, United States, 1 Jan 2023 – 11 Oct 2026. Monitor data from AirNow, via OpenAQ and from the publisher directly; sources listed at smogrank.com/sources. smogrank.com/us/decatur-alabama/history (accessed 13 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.
Decatur now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-13 04:07 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).