Milwaukee Air Quality in 2021
In 2021, Milwaukee's air quality (Milwaukee-Waukesha-West Allis, WI area) had a median daily AQI of 53 (Moderate) across 365 monitored days. 12 days (3.3%) reached Unhealthy for Sensitive Groups or worse, 149 were Good, and the year's peak AQI was 129 (Unhealthy for Sensitive Groups). Fine particulate matter (PM2.5) set the daily AQI on 234 of those days. The cleanest month of 2021 was October (median AQI 42, 0 days above 100) and the worst was June (median 57, 5 days above 100, peak 112).
- Good: 40.8%
- Moderate: 55.9%
- Unhealthy for Sensitive Groups: 3.3%
- Unhealthy or worse: 0.0%
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How was Milwaukee's air quality in 2021?
Moderate on a typical day: median AQI 53, with 12 days above AQI 100 out of 365 monitored — the 5th cleanest of 7 years on record for the area.
- ✓Peak AQI in 2021: 129 (Unhealthy for Sensitive Groups).
- ✓Fine particulate matter (PM2.5) was the main pollutant on 234 days.
- ✓Cleanest month: October; worst: June.
Frequently asked questions
What was the average AQI in Milwaukee in 2021?▾
EPA's Air Quality System puts Milwaukee's (Milwaukee-Waukesha-West Allis, WI) median daily AQI for 2021 at 53, which is Moderate. 12 days were Unhealthy for Sensitive Groups or worse and the year's highest AQI was 129.
Which month had the worst air quality in Milwaukee in 2021?▾
The cleanest month of 2021 was October (median AQI 42, 0 days above 100) and the worst was June (median 57, 5 days above 100, peak 112).
Was 2021 a good or bad year for Milwaukee's air?▾
Among the 7 years EPA has published for the area (2019–2025), 2021 ranks 5th cleanest by days above AQI 100. 2021's median of 53 is above the area's typical annual median of 49.
Milwaukee month by month in 2021
Milwaukee air quality month by month, 2021 (Milwaukee-Waukesha-West Allis, WI, EPA AQS daily AQI)
| Month | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| January | 31 | 55 | 0 | 78 | PM2.5 |
| February | 28 | 58 | 0 | 95 | PM2.5 |
| March | 31 | 54 | 0 | 95 | PM2.5 |
| April | 30 | 48 | 1 | 109 | PM2.5 |
| May | 31 | 47 | 0 | 85 | O3 |
| Juneworst | 30 | 57 | 5 | 112 | O3 |
| July | 31 | 60 | 3 | 115 | PM2.5 |
| August | 31 | 61 | 3 | 129 | PM2.5 |
| September | 30 | 45 | 0 | 77 | O3 |
| Octobercleanest | 31 | 42 | 0 | 80 | PM2.5 |
| November | 30 | 49 | 0 | 74 | PM2.5 |
| December | 31 | 54 | 0 | 84 | PM2.5 |
How 2021 compares
Among the 7 years EPA has published for the area (2019–2025), 2021 ranks 5th cleanest by days above AQI 100.
2021's median of 53 is above the area's typical annual median of 49.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Milwaukee
The latest EPA AirNow observation puts Milwaukee's AQI at 22 (PM2.5). The figures above are multi-year annual statistics, not today's reading.
View current Milwaukee air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Milwaukee-Waukesha-West Allis, 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.