SmogRank / United States / Illinois / Chicago
Chicago, month by month
Chicago has a measured daily mean on 1,316 days since 1 January 2023. Its worst month was July 2026, at 79 US AQI (24.3 µg/m³), 230th of 2,784 cities on that month's world ranking. Its cleanest was May 2025, at 34 US AQI (6.1 µg/m³). 2025 averaged 52 US AQI (9.6 µg/m³), against 44 US AQI (8.0 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
2 months
| Month | Why |
|---|---|
| Mar 2023 | 11 of 31 days measured; a month needs 22. The others: 20 missing from OpenAQ's archive. |
| Feb 2023 | 3 of 28 days measured; a month needs 20. The others: 25 missing from OpenAQ's archive. |
A day counts once 18 hours of it are measured; a month needs 70% of its days.
Chicago's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| July 2026 | 7924.3 µg/m³ | 230thof 2,784 | Northern United States and Canada, July 2026 |
| June 2023 | 7722.9 µg/m³ | 218thof 1,603 | Eastern United States and Canada, June and July 2023 United States and Canada, June 2023 |
| June 2025 | 6416.1 µg/m³ | 363rdof 2,508 | Northern United States and Canada, June 2025 Northern United States and Canada, May and June 2025 |
| July 2025 | 6215.2 µg/m³ | 388thof 2,889 | North-eastern United States and Canada, 29 July to 9 August 2025 Northern United States, July 2025and 1 more |
| July 2023 | 6013.7 µg/m³ | 222ndof 1,432 | Northern United States and Canada, July 2023 United States and Canada, July 2023and 2 more |
| August 2025 | 5913.4 µg/m³ | 508thof 2,901 | North-eastern United States and Canada, 29 July to 9 August 2025 |
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.
Chicago's worst days
| Day | US AQI | Episode |
|---|---|---|
| 16 Jul 2026 | 316233.0 µg/m³ | Northern United States and Canada, July 2026 |
| 17 Jul 2026 | 190111.0 µg/m³ | Northern United States and Canada, July 2026 |
| 28 Jun 2023 | 17691.7 µg/m³ | Eastern United States and Canada, June and July 2023 |
| 27 Jun 2023 | 17691.3 µg/m³ | Eastern United States and Canada, June and July 2023 |
| 31 Jul 2025 | 16169.7 µg/m³ | North-eastern United States and Canada, 29 July to 9 August 2025 |
| 5 Jun 2025 | 15358.4 µg/m³ | Northern United States and Canada, May and June 2025 |
| 29 Jun 2023 | 14453.1 µg/m³ | Eastern United States and Canada, June and July 2023 |
| 19 Jul 2026 | 14051.3 µg/m³ | Northern United States and Canada, July 2026 |
| 1 Aug 2025 | 13247.9 µg/m³ | North-eastern United States and Canada, 29 July to 9 August 2025 |
| 20 Jul 2026 | 12043.4 µg/m³ | Northern United States and Canada, July 2026 |
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, Chicago, 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/chicago/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.
Chicago now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-12 17:07 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).