Milwaukee Air Quality in May
Across 2019–2025, Milwaukee's May air quality had a median AQI of 45 (Good) over 217 monitored days in the Milwaukee-Waukesha-West Allis, WI area. 4.1% of May days (9 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 2025 (median AQI 40, 0 days above 100) and the worst was 2023 (median 61, 6 days above 100, peak AQI 126).
- Good: 61.3%
- Moderate: 34.6%
- Unhealthy for Sensitive Groups: 4.1%
- Unhealthy or worse: 0.0%
Reduce Indoor Ozone in Milwaukee
Today's main pollutant in Milwaukee is ground-level ozone (AQI 32). Important: standard HEPA filters do NOT remove ozone — only a purifier with a substantial activated-carbon bed adsorbs it. The biggest wins are cutting indoor sources (gas appliances, certain "ionizer" purifiers) and ventilating when outdoor ozone is low (early morning). A high-carbon unit helps with the gases and VOCs that linger indoors.
Recommended: Levoit Core 300 — True HEPA + activated carbon · CADR ~141 CFM · rooms up to 219 sq ft
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How is the air in Milwaukee in May?
Good on a typical day: median AQI 45 across 2019–2025, with 4.1% of May days above AQI 100. Ground-level ozone is the main driver.
- ✓61.3% of May days were Good (AQI 0–50), 34.6% Moderate (51–100).
- ✓9 days of 217 reached AQI 101+; the May peak was 126.
- ✓Best May: 2025; worst May: 2023.
Frequently asked questions
What is the air quality like in Milwaukee in May?▾
Across 2019–2025, the median daily AQI in Milwaukee in May was 45 (Good). 61.3% of days were Good, 34.6% Moderate, and 4.1% 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 Milwaukee?▾
A typical May day in Milwaukee sits in the Good range (median AQI 45), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 24 of May days (4.1%) reached AQI 101+ in 2019–2025.
Which pollutant causes Milwaukee's May air quality problems?▾
Ground-level ozone set the daily AQI on 72.4% of May days in Milwaukee. The highest May AQI recorded in 2019–2025 was 126 (Unhealthy for Sensitive Groups), in 2023.
Milwaukee May air quality, year by year
Milwaukee May air quality by year (Milwaukee-Waukesha-West Allis, WI, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 31 | 43 | 0 | 77 | O3 |
| 2020 | 31 | 41 | 0 | 74 | O3 |
| 2021 | 31 | 47 | 0 | 85 | O3 |
| 2022 | 31 | 49 | 2 | 126 | O3 |
| 2023worst | 31 | 61 | 6 | 126 | O3 |
| 2024 | 31 | 45 | 1 | 101 | O3 |
| 2025cleanest | 31 | 40 | 0 | 97 | O3 |
What May air means in Milwaukee
A typical May day in Milwaukee sits in the Good range (median AQI 45), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 24 of May days (4.1%) reached AQI 101+ in 2019–2025.
May's median AQI of 45 is below Milwaukee's whole-year median of 49, making it one of the area's cleaner periods. Nationally, the median May AQI across every EPA metro area (104,064 metro-days, 2019–2025) is 44, so Milwaukee runs in line with the national May norm; 4.1% of its May days topped AQI 100 versus 1.3% nationally (above average).
May is part of Milwaukee's spring season (March, April, May); the spring page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Milwaukee
The latest EPA AirNow observation puts Milwaukee's AQI at 32 (O3). The figures above are multi-year month 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.