SmogRank / United States / Illinois / Upper Alton
Upper Alton, month by month
Upper Alton has a measured daily mean on 736 days since 1 February 2024. Its worst month was July 2026, at 61 US AQI (14.4 µg/m³), 560th of 2,784 cities on that month's world ranking. Its cleanest was May 2025, at 32 US AQI (5.7 µg/m³).
Every month since 2024
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
9 months
| Month | Why |
|---|---|
| Jan 2025 | 21 of 31 days measured; a month needs 22. The others: 10 with under 18 hours of readings or readings that failed our checks. |
| Sep 2024 | 11 of 30 days measured; a month needs 21. The others: 19 with under 18 hours of readings or readings that failed our checks. |
| Aug 2024 | No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks. |
| Jul 2024 | No day measured. The others: 31 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 | No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks. |
| Apr 2024 | No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks. |
| Mar 2024 | 1 of 31 days measured; a month needs 22. The others: 30 with under 18 hours of readings or readings that failed our checks. |
| Feb 2024 | 1 of 29 days measured; a month needs 21. The others: 28 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.
Upper Alton's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| July 2026 | 6114.4 µg/m³ | 560thof 2,784 | Northern United States and Canada, July 2026 North-eastern United States, June and July 2026 |
| June 2025 | 5812.6 µg/m³ | 717thof 2,508 | Northern United States and Canada, June 2025 Northern United States and Canada, May and June 2025 |
| August 2026 | 5511.2 µg/m³ | 667thof 2,896 | – |
| August 2025 | 5410.6 µg/m³ | 1,099thof 2,901 | North-eastern United States and Canada, 29 July to 9 August 2025 |
| July 2025 | 5310.1 µg/m³ | 1,244thof 2,889 | North-eastern United States and Canada, 29 July to 9 August 2025 North-eastern United States, July 2025 |
| October 2024 | 5310.0 µg/m³ | 524thof 2,020 | – |
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.
Upper Alton's worst days
| Day | US AQI | Episode |
|---|---|---|
| 15 Mar 2025 | 15358.6 µg/m³ | Eastern United States, March 2025 |
| 20 Jul 2026 | 14352.7 µg/m³ | Northern United States and Canada, July 2026 |
| 1 Aug 2025 | 13248.1 µg/m³ | North-eastern United States and Canada, 29 July to 9 August 2025 |
| 7 Jun 2025 | 9331.5 µg/m³ | Northern United States and Canada, May and June 2025 |
| 30 Jun 2026 | 9029.8 µg/m³ | North-eastern United States, June and July 2026 |
| 11 Jun 2025 | 8426.6 µg/m³ | Northern United States and Canada, June 2025 |
| 12 Jun 2025 | 8225.9 µg/m³ | Northern United States and Canada, June 2025 |
| 5 Jul 2025 | 8125.4 µg/m³ | North-eastern United States, July 2025 |
| 4 Jul 2025 | 7823.6 µg/m³ | North-eastern United States, July 2025 |
| 21 Oct 2024 | 7522.1 µg/m³ | – |
Daily means, the highest since 1 Feb 2024; 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, Upper Alton, United States, 1 Feb 2024 – 11 Oct 2026. Monitor data from AirNow, via OpenAQ and from the publisher directly; sources listed at smogrank.com/sources. smogrank.com/us/upper-alton/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.
Upper Alton now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-12 20:07 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).