Rockford Air Quality in September
Across 2019–2025, Rockford's September air quality had a median AQI of 44 (Good) over 210 monitored days in the Rockford, IL area. 1.9% of September days (4 of 210) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 53.3% of days. The cleanest September on record here was 2019 (median AQI 37, 0 days above 100) and the worst was 2024 (median 44, 3 days above 100, peak AQI 119).
- Good: 62.9%
- Moderate: 35.2%
- Unhealthy for Sensitive Groups: 1.9%
- Unhealthy or worse: 0.0%
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How is the air in Rockford in September?
Good on a typical day: median AQI 44 across 2019–2025, with 1.9% of September days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓62.9% of September days were Good (AQI 0–50), 35.2% Moderate (51–100).
- ✓4 days of 210 reached AQI 101+; the September peak was 119.
- ✓Best September: 2019; worst September: 2024.
Frequently asked questions
What is the air quality like in Rockford in September?▾
Across 2019–2025, the median daily AQI in Rockford in September was 44 (Good). 62.9% of days were Good, 35.2% Moderate, and 1.9% reached Unhealthy for Sensitive Groups or worse, based on 210 monitored days in EPA's Air Quality System.
Is September a good time for outdoor exercise in Rockford?▾
A typical September day in Rockford sits in the Good range (median AQI 44), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 53 of September days (1.9%) reached AQI 101+ in 2019–2025.
Which pollutant causes Rockford's September air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 53.3% of September days in Rockford. The highest September AQI recorded in 2019–2025 was 119 (Unhealthy for Sensitive Groups), in 2024.
Rockford September air quality, year by year
Rockford September air quality by year (Rockford, IL, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019cleanest | 30 | 37 | 0 | 61 | O3 |
| 2020 | 30 | 41 | 0 | 65 | PM2.5 |
| 2021 | 30 | 45 | 0 | 87 | O3 |
| 2022 | 30 | 37 | 0 | 56 | PM2.5 |
| 2023 | 30 | 52 | 0 | 71 | PM2.5 |
| 2024worst | 30 | 44 | 3 | 119 | O3 |
| 2025 | 30 | 52 | 1 | 112 | O3 |
What September air means in Rockford
A typical September day in Rockford sits in the Good range (median AQI 44), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 53 of September days (1.9%) reached AQI 101+ in 2019–2025.
September's median AQI of 44 is in line with Rockford's whole-year median of 47, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median September AQI across every EPA metro area (100,699 metro-days, 2019–2025) is 43, so Rockford runs in line with the national September norm; 1.9% of its September days topped AQI 100 versus 2.7% nationally (about the same).
September is part of Rockford's fall season (September, October, November); the fall page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Rockford
The latest EPA AirNow observation puts Rockford's AQI at 22 (PM2.5). The figures above are multi-year month statistics, not today's reading.
View current Rockford air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Rockford, IL), 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.