Chicago Air Quality in 2019
In 2019, Chicago's air quality (Chicago-Naperville-Elgin, IL-IN-WI area) had a median daily AQI of 60 (Moderate) across 365 monitored days. 13 days (3.6%) reached Unhealthy for Sensitive Groups or worse, 53 were Good, and the year's peak AQI was 174 (Unhealthy). Fine particulate matter (PM2.5) set the daily AQI on 292 of those days. The cleanest month of 2019 was October (median AQI 55, 0 days above 100) and the worst was July (median 73, 7 days above 100, peak 129).
- Good: 14.5%
- Moderate: 81.9%
- Unhealthy for Sensitive Groups: 3.3%
- Unhealthy or worse: 0.3%
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How was Chicago's air quality in 2019?
Moderate on a typical day: median AQI 60, with 13 days above AQI 100 out of 365 monitored — the 1st cleanest of 7 years on record for the area.
- ✓Peak AQI in 2019: 174 (Unhealthy).
- ✓Fine particulate matter (PM2.5) was the main pollutant on 292 days.
- ✓Cleanest month: October; worst: July.
Frequently asked questions
What was the average AQI in Chicago in 2019?▾
EPA's Air Quality System puts Chicago's (Chicago-Naperville-Elgin, IL-IN-WI) median daily AQI for 2019 at 60, which is Moderate. 13 days were Unhealthy for Sensitive Groups or worse and the year's highest AQI was 174.
Which month had the worst air quality in Chicago in 2019?▾
The cleanest month of 2019 was October (median AQI 55, 0 days above 100) and the worst was July (median 73, 7 days above 100, peak 129).
Was 2019 a good or bad year for Chicago's air?▾
Among the 7 years EPA has published for the area (2019–2025), 2019 ranks 1st cleanest by days above AQI 100 — the best year on record here. 2019's median of 60 is in line with the area's typical annual median of 60.
Chicago month by month in 2019
Chicago air quality month by month, 2019 (Chicago-Naperville-Elgin, IL-IN-WI, EPA AQS daily AQI)
| Month | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| January | 31 | 58 | 0 | 74 | PM2.5 |
| February | 28 | 58 | 0 | 89 | PM2.5 |
| March | 31 | 60 | 0 | 97 | PM2.5 |
| April | 30 | 56 | 0 | 97 | PM2.5 |
| May | 31 | 59 | 0 | 84 | PM2.5 |
| June | 30 | 69 | 4 | 129 | PM2.5 |
| Julyworst | 31 | 73 | 7 | 129 | PM2.5 |
| August | 31 | 59 | 2 | 174 | PM2.5 |
| September | 30 | 58 | 0 | 93 | PM2.5 |
| Octobercleanest | 31 | 55 | 0 | 73 | PM2.5 |
| November | 30 | 62 | 0 | 85 | PM2.5 |
| December | 31 | 64 | 0 | 91 | PM2.5 |
How 2019 compares
Among the 7 years EPA has published for the area (2019–2025), 2019 ranks 1st cleanest by days above AQI 100 — the best year on record here.
2019's median of 60 is in line with 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 41 (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.