Chicago Air Quality in 2025
In 2025, Chicago's air quality (Chicago-Naperville-Elgin, IL-IN-WI area) had a median daily AQI of 56 (Moderate) across 365 monitored days. 32 days (8.8%) reached Unhealthy for Sensitive Groups or worse, 109 were Good, and the year's peak AQI was 219 (Very Unhealthy). Fine particulate matter (PM2.5) set the daily AQI on 234 of those days. The cleanest month of 2025 was May (median AQI 51, 0 days above 100) and the worst was July (median 77, 9 days above 100, peak 168).
- Good: 29.9%
- Moderate: 61.4%
- Unhealthy for Sensitive Groups: 7.1%
- Unhealthy or worse: 1.6%
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How was Chicago's air quality in 2025?
Moderate on a typical day: median AQI 56, with 32 days above AQI 100 out of 365 monitored — the 6th cleanest of 7 years on record for the area.
- ✓Peak AQI in 2025: 219 (Very Unhealthy).
- ✓Fine particulate matter (PM2.5) was the main pollutant on 234 days.
- ✓Cleanest month: May; worst: July.
Frequently asked questions
What was the average AQI in Chicago in 2025?▾
EPA's Air Quality System puts Chicago's (Chicago-Naperville-Elgin, IL-IN-WI) median daily AQI for 2025 at 56, which is Moderate. 32 days were Unhealthy for Sensitive Groups or worse and the year's highest AQI was 219.
Which month had the worst air quality in Chicago in 2025?▾
The cleanest month of 2025 was May (median AQI 51, 0 days above 100) and the worst was July (median 77, 9 days above 100, peak 168).
Was 2025 a good or bad year for Chicago's air?▾
Among the 7 years EPA has published for the area (2019–2025), 2025 ranks 6th cleanest by days above AQI 100. 2025's median of 56 is below the area's typical annual median of 60.
Chicago month by month in 2025
Chicago air quality month by month, 2025 (Chicago-Naperville-Elgin, IL-IN-WI, EPA AQS daily AQI)
| Month | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| January | 31 | 54 | 0 | 79 | PM2.5 |
| February | 28 | 56 | 0 | 67 | PM2.5 |
| March | 31 | 50 | 1 | 137 | PM2.5 |
| April | 30 | 53 | 2 | 219 | PM2.5 |
| Maycleanest | 31 | 51 | 0 | 97 | PM2.5 |
| June | 30 | 81 | 8 | 154 | O3 |
| Julyworst | 31 | 77 | 9 | 168 | O3 |
| August | 31 | 54 | 7 | 144 | PM2.5 |
| September | 30 | 63 | 4 | 147 | O3 |
| October | 31 | 47 | 1 | 122 | PM2.5 |
| November | 30 | 55 | 0 | 84 | PM2.5 |
| December | 31 | 60 | 0 | 76 | PM2.5 |
How 2025 compares
Among the 7 years EPA has published for the area (2019–2025), 2025 ranks 6th cleanest by days above AQI 100.
2025'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.