Rockford Air Quality in May
Across 2019–2025, Rockford's May air quality had a median AQI of 44 (Good) over 217 monitored days in the Rockford, IL area. 1.4% of May days (3 of 217) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 72.4% of days. The cleanest May on record here was 2020 (median AQI 41, 0 days above 100) and the worst was 2023 (median 59, 3 days above 100, peak AQI 133).
- Good: 67.7%
- Moderate: 30.9%
- Unhealthy for Sensitive Groups: 1.4%
- Unhealthy or worse: 0.0%
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How is the air in Rockford in May?
Good on a typical day: median AQI 44 across 2019–2025, with 1.4% of May days above AQI 100. Ground-level ozone is the main driver.
- ✓67.7% of May days were Good (AQI 0–50), 30.9% Moderate (51–100).
- ✓3 days of 217 reached AQI 101+; the May peak was 133.
- ✓Best May: 2020; worst May: 2023.
Frequently asked questions
What is the air quality like in Rockford in May?▾
Across 2019–2025, the median daily AQI in Rockford in May was 44 (Good). 67.7% of days were Good, 30.9% Moderate, and 1.4% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is May a good time for outdoor exercise in Rockford?▾
A typical May 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 71 of May days (1.4%) reached AQI 101+ in 2019–2025.
Which pollutant causes Rockford's May air quality problems?▾
Ground-level ozone set the daily AQI on 72.4% of May days in Rockford. The highest May AQI recorded in 2019–2025 was 133 (Unhealthy for Sensitive Groups), in 2023.
Rockford May air quality, year by year
Rockford May air quality by year (Rockford, IL, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 31 | 42 | 0 | 77 | O3 |
| 2020cleanest | 31 | 41 | 0 | 55 | O3 |
| 2021 | 31 | 43 | 0 | 67 | O3 |
| 2022 | 31 | 43 | 0 | 77 | O3 |
| 2023worst | 31 | 59 | 3 | 133 | O3 |
| 2024 | 31 | 46 | 0 | 71 | O3 |
| 2025 | 31 | 41 | 0 | 80 | O3 |
What May air means in Rockford
A typical May 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 71 of May days (1.4%) reached AQI 101+ in 2019–2025.
May'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 May AQI across every EPA metro area (104,064 metro-days, 2019–2025) is 44, so Rockford runs in line with the national May norm; 1.4% of its May days topped AQI 100 versus 1.3% nationally (about the same).
May is part of Rockford's spring season (March, April, May); the spring 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.