Chicago Air Quality in July
Across 2019–2025, Chicago's July air quality had a median AQI of 71 (Moderate) over 217 monitored days in the Chicago-Naperville-Elgin, IL-IN-WI area. 23.5% of July days (51 of 217) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 51.2% of days. The cleanest July on record here was 2024 (median AQI 69, 3 days above 100) and the worst was 2020 (median 74, 11 days above 100, peak AQI 156).
- Good: 8.8%
- Moderate: 67.7%
- Unhealthy for Sensitive Groups: 19.4%
- Unhealthy or worse: 4.1%
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How is the air in Chicago in July?
Moderate on a typical day: median AQI 71 across 2019–2025, with 23.5% of July days above AQI 100. Ground-level ozone is the main driver.
- ✓8.8% of July days were Good (AQI 0–50), 67.7% Moderate (51–100).
- ✓51 days of 217 reached AQI 101+; the July peak was 192.
- ✓Best July: 2024; worst July: 2020.
Frequently asked questions
What is the air quality like in Chicago in July?▾
Across 2019–2025, the median daily AQI in Chicago in July was 71 (Moderate). 8.8% of days were Good, 67.7% Moderate, and 23.5% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is July a good time for outdoor exercise in Chicago?▾
A typical July day in Chicago is Moderate (median AQI 71): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 4 of July days (23.5%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Which pollutant causes Chicago's July air quality problems?▾
Ground-level ozone set the daily AQI on 51.2% of July days in Chicago. The highest July AQI recorded in 2019–2025 was 192 (Unhealthy), in 2020.
Chicago July air quality, year by year
Chicago July air quality by year (Chicago-Naperville-Elgin, IL-IN-WI, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 31 | 73 | 7 | 129 | PM2.5 |
| 2020worst | 31 | 74 | 11 | 156 | O3 |
| 2021 | 31 | 68 | 7 | 136 | PM2.5 |
| 2022 | 31 | 61 | 4 | 122 | PM2.5 |
| 2023 | 31 | 74 | 10 | 192 | O3 |
| 2024cleanest | 31 | 69 | 3 | 136 | O3 |
| 2025 | 31 | 77 | 9 | 168 | O3 |
What July air means in Chicago
A typical July day in Chicago is Moderate (median AQI 71): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 4 of July days (23.5%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
July's median AQI of 71 is above Chicago's whole-year median of 60, making it one of the area's dirtier periods. Nationally, the median July AQI across every EPA metro area (103,858 metro-days, 2019–2025) is 47, so Chicago runs above the national July norm; 23.5% of its July days topped AQI 100 versus 3.6% nationally (above average).
July is part of Chicago's summer season (June, July, August); the summer page pools all three months.
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 month 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.