Chicago Air Quality in 2024
In 2024, Chicago's air quality (Chicago-Naperville-Elgin, IL-IN-WI area) had a median daily AQI of 56 (Moderate) across 366 monitored days. 17 days (4.6%) reached Unhealthy for Sensitive Groups or worse, 95 were Good, and the year's peak AQI was 166 (Unhealthy). Fine particulate matter (PM2.5) set the daily AQI on 213 of those days. The cleanest month of 2024 was April (median AQI 50, 0 days above 100) and the worst was August (median 61, 5 days above 100, peak 166).
- Good: 26.0%
- Moderate: 69.4%
- Unhealthy for Sensitive Groups: 4.1%
- Unhealthy or worse: 0.5%
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How was Chicago's air quality in 2024?
Moderate on a typical day: median AQI 56, with 17 days above AQI 100 out of 366 monitored — the 3rd cleanest of 7 years on record for the area.
- ✓Peak AQI in 2024: 166 (Unhealthy).
- ✓Fine particulate matter (PM2.5) was the main pollutant on 213 days.
- ✓Cleanest month: April; worst: August.
Frequently asked questions
What was the average AQI in Chicago in 2024?▾
EPA's Air Quality System puts Chicago's (Chicago-Naperville-Elgin, IL-IN-WI) median daily AQI for 2024 at 56, which is Moderate. 17 days were Unhealthy for Sensitive Groups or worse and the year's highest AQI was 166.
Which month had the worst air quality in Chicago in 2024?▾
The cleanest month of 2024 was April (median AQI 50, 0 days above 100) and the worst was August (median 61, 5 days above 100, peak 166).
Was 2024 a good or bad year for Chicago's air?▾
Among the 7 years EPA has published for the area (2019–2025), 2024 ranks 3rd cleanest by days above AQI 100. 2024's median of 56 is below the area's typical annual median of 60.
Chicago month by month in 2024
Chicago air quality month by month, 2024 (Chicago-Naperville-Elgin, IL-IN-WI, EPA AQS daily AQI)
| Month | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| January | 31 | 56 | 0 | 81 | PM2.5 |
| February | 29 | 58 | 0 | 91 | PM2.5 |
| March | 31 | 53 | 1 | 166 | PM2.5 |
| Aprilcleanest | 30 | 50 | 0 | 74 | O3 |
| May | 31 | 57 | 0 | 97 | O3 |
| June | 30 | 68 | 3 | 143 | O3 |
| July | 31 | 69 | 3 | 136 | O3 |
| Augustworst | 31 | 61 | 5 | 166 | O3 |
| September | 30 | 74 | 4 | 115 | O3 |
| October | 31 | 59 | 0 | 92 | PM2.5 |
| November | 30 | 52 | 0 | 73 | PM2.5 |
| December | 31 | 55 | 1 | 111 | PM2.5 |
How 2024 compares
Among the 7 years EPA has published for the area (2019–2025), 2024 ranks 3rd cleanest by days above AQI 100.
2024's median of 56 is below the area's typical annual median of 60.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Chicago
The latest EPA AirNow observation puts Chicago's AQI at 46 (PM2.5). The figures above are multi-year annual statistics, not today's reading.
View current Chicago air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Chicago-Naperville-Elgin, IL-IN-WI), 2019–2025. Daily AQI per CBSA is the highest AQI reported by any monitor in the area that day; the defining parameter is the pollutant that set it. Month and season statistics pool every such day in the period across all years listed. Retrieved 2026-09-09.