Milwaukee Air Quality in January
Across 2019–2025, Milwaukee's January air quality had a median AQI of 53 (Moderate) over 217 monitored days in the Milwaukee-Waukesha-West Allis, WI area. 0.0% of January days (0 of 217) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 88.0% of days. The cleanest January on record here was 2025 (median AQI 38, 0 days above 100) and the worst was 2023 (median 57, 0 days above 100, peak AQI 92).
- Good: 44.2%
- Moderate: 55.8%
- Unhealthy for Sensitive Groups: 0.0%
- 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 January?
Moderate on a typical day: median AQI 53 across 2019–2025, with 0.0% of January days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓44.2% of January days were Good (AQI 0–50), 55.8% Moderate (51–100).
- ✓0 days of 217 reached AQI 101+; the January peak was 92.
- ✓Best January: 2025; worst January: 2023.
Frequently asked questions
What is the air quality like in Milwaukee in January?▾
Across 2019–2025, the median daily AQI in Milwaukee in January was 53 (Moderate). 44.2% of days were Good, 55.8% Moderate, and 0.0% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is January a good time for outdoor exercise in Milwaukee?▾
A typical January day in Milwaukee is Moderate (median AQI 53): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and fewer than 1% of January days reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Which pollutant causes Milwaukee's January air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 88.0% of January days in Milwaukee. The highest January AQI recorded in 2019–2025 was 92 (Moderate), in 2023.
Milwaukee January air quality, year by year
Milwaukee January 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 | 54 | 0 | 71 | PM2.5 |
| 2020 | 31 | 53 | 0 | 79 | PM2.5 |
| 2021 | 31 | 55 | 0 | 78 | PM2.5 |
| 2022 | 31 | 55 | 0 | 92 | PM2.5 |
| 2023worst | 31 | 57 | 0 | 92 | PM2.5 |
| 2024 | 31 | 48 | 0 | 70 | PM2.5 |
| 2025cleanest | 31 | 38 | 0 | 76 | PM2.5 |
What January air means in Milwaukee
A typical January day in Milwaukee is Moderate (median AQI 53): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and fewer than 1% of January days reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
January's median AQI of 53 is above Milwaukee's whole-year median of 49, making it one of the area's dirtier periods. Nationally, the median January AQI across every EPA metro area (95,602 metro-days, 2019–2025) is 39, so Milwaukee runs above the national January norm; 0.0% of its January days topped AQI 100 versus 0.7% nationally (about the same).
January is part of Milwaukee's winter season (December, January, February); the winter 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.