Rockford Air Quality in December
Across 2019–2025, Rockford's December air quality had a median AQI of 48 (Good) over 207 monitored days in the Rockford, IL area. 0.0% of December days (0 of 207) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 100.0% of days. The cleanest December on record here was 2024 (median AQI 40, 0 days above 100) and the worst was 2019 (median 57, 0 days above 100, peak AQI 83).
- Good: 52.7%
- Moderate: 47.3%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
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How is the air in Rockford in December?
Good on a typical day: median AQI 48 across 2019–2025, with 0.0% of December days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓52.7% of December days were Good (AQI 0–50), 47.3% Moderate (51–100).
- ✓0 days of 207 reached AQI 101+; the December peak was 87.
- ✓Best December: 2024; worst December: 2019.
Frequently asked questions
What is the air quality like in Rockford in December?▾
Across 2019–2025, the median daily AQI in Rockford in December was 48 (Good). 52.7% of days were Good, 47.3% Moderate, and 0.0% reached Unhealthy for Sensitive Groups or worse, based on 207 monitored days in EPA's Air Quality System.
Is December a good time for outdoor exercise in Rockford?▾
A typical December day in Rockford sits in the Good range (median AQI 48), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of December days reached AQI 101+ in 2019–2025.
Which pollutant causes Rockford's December air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 100.0% of December days in Rockford. The highest December AQI recorded in 2019–2025 was 87 (Moderate), in 2019.
Rockford December air quality, year by year
Rockford December air quality by year (Rockford, IL, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019worst | 27 | 57 | 0 | 83 | PM2.5 |
| 2020 | 31 | 53 | 0 | 87 | PM2.5 |
| 2021 | 30 | 50 | 0 | 67 | PM2.5 |
| 2022 | 31 | 51 | 0 | 82 | PM2.5 |
| 2023 | 31 | 42 | 0 | 68 | PM2.5 |
| 2024cleanest | 26 | 40 | 0 | 62 | PM2.5 |
| 2025 | 31 | 46 | 0 | 66 | PM2.5 |
What December air means in Rockford
A typical December day in Rockford sits in the Good range (median AQI 48), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of December days reached AQI 101+ in 2019–2025.
December's median AQI of 48 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 December AQI across every EPA metro area (95,590 metro-days, 2019–2025) is 39, so Rockford runs above the national December norm; 0.0% of its December days topped AQI 100 versus 0.7% nationally (about the same).
December is part of Rockford's winter season (December, January, February); the winter 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.