Chicago Air Quality in August
Across 2019–2025, Chicago's August air quality had a median AQI of 62 (Moderate) over 217 monitored days in the Chicago-Naperville-Elgin, IL-IN-WI area. 13.3% of August days (29 of 217) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 53.9% of days. The cleanest August on record here was 2022 (median AQI 54, 0 days above 100) and the worst was 2021 (median 71, 7 days above 100, peak AQI 156).
- Good: 15.2%
- Moderate: 71.4%
- Unhealthy for Sensitive Groups: 11.5%
- Unhealthy or worse: 1.8%
Improve Indoor Air Quality
Even with good outdoor air in Chicago, indoor PM2.5, dust and allergens build up. A True-HEPA purifier keeps a bedroom or office consistently clean.
Recommended: Levoit Core 400S — True HEPA · CADR ~141 CFM · rooms up to 219 sq ft
As an Amazon Associate, we earn from qualifying purchases.
How is the air in Chicago in August?
Moderate on a typical day: median AQI 62 across 2019–2025, with 13.3% of August days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓15.2% of August days were Good (AQI 0–50), 71.4% Moderate (51–100).
- ✓29 days of 217 reached AQI 101+; the August peak was 174.
- ✓Best August: 2022; worst August: 2021.
Frequently asked questions
What is the air quality like in Chicago in August?▾
Across 2019–2025, the median daily AQI in Chicago in August was 62 (Moderate). 15.2% of days were Good, 71.4% Moderate, and 13.3% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is August a good time for outdoor exercise in Chicago?▾
A typical August day in Chicago is Moderate (median AQI 62): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 8 of August days (13.3%) 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 August air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 53.9% of August days in Chicago. The highest August AQI recorded in 2019–2025 was 174 (Unhealthy), in 2021.
Chicago August air quality, year by year
Chicago August 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 | 59 | 2 | 174 | PM2.5 |
| 2020 | 31 | 63 | 3 | 129 | PM2.5 |
| 2021worst | 31 | 71 | 7 | 156 | O3 |
| 2022cleanest | 31 | 54 | 0 | 77 | PM2.5 |
| 2023 | 31 | 70 | 5 | 166 | PM2.5 |
| 2024 | 31 | 61 | 5 | 166 | O3 |
| 2025 | 31 | 54 | 7 | 144 | PM2.5 |
What August air means in Chicago
A typical August day in Chicago is Moderate (median AQI 62): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 8 of August days (13.3%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
August's median AQI of 62 is in line with Chicago's whole-year median of 60, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median August AQI across every EPA metro area (104,152 metro-days, 2019–2025) is 45, so Chicago runs above the national August norm; 13.3% of its August days topped AQI 100 versus 3.5% nationally (above average).
August 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 43 (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.