Ann Arbor Air Quality in January
Across 2019–2025, Ann Arbor's January air quality had a median AQI of 45 (Good) over 217 monitored days in the Ann Arbor, MI 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 75.1% of days. The cleanest January on record here was 2025 (median AQI 34, 0 days above 100) and the worst was 2023 (median 55, 0 days above 100, peak AQI 83).
- Good: 57.6%
- Moderate: 42.4%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
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How is the air in Ann Arbor in January?
Good on a typical day: median AQI 45 across 2019–2025, with 0.0% of January days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓57.6% of January days were Good (AQI 0–50), 42.4% Moderate (51–100).
- ✓0 days of 217 reached AQI 101+; the January peak was 83.
- ✓Best January: 2025; worst January: 2023.
Frequently asked questions
What is the air quality like in Ann Arbor in January?▾
Across 2019–2025, the median daily AQI in Ann Arbor in January was 45 (Good). 57.6% of days were Good, 42.4% 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 Ann Arbor?▾
A typical January day in Ann Arbor sits in the Good range (median AQI 45), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of January days reached AQI 101+ in 2019–2025.
Which pollutant causes Ann Arbor's January air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 75.1% of January days in Ann Arbor. The highest January AQI recorded in 2019–2025 was 83 (Moderate), in 2023.
Ann Arbor January air quality, year by year
Ann Arbor January air quality by year (Ann Arbor, MI, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 31 | 51 | 0 | 63 | PM2.5 |
| 2020 | 31 | 37 | 0 | 71 | PM2.5 |
| 2021 | 31 | 48 | 0 | 68 | PM2.5 |
| 2022 | 31 | 52 | 0 | 81 | PM2.5 |
| 2023worst | 31 | 55 | 0 | 83 | PM2.5 |
| 2024 | 31 | 39 | 0 | 73 | PM2.5 |
| 2025cleanest | 31 | 34 | 0 | 75 | O3 |
What January air means in Ann Arbor
A typical January day in Ann Arbor sits in the Good range (median AQI 45), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of January days reached AQI 101+ in 2019–2025.
January's median AQI of 45 is in line with Ann Arbor's whole-year median of 44, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median January AQI across every EPA metro area (95,602 metro-days, 2019–2025) is 39, so Ann Arbor 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 Ann Arbor's winter season (December, January, February); the winter page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Ann Arbor
The latest EPA AirNow observation puts Ann Arbor's AQI at 29 (PM2.5). The figures above are multi-year month statistics, not today's reading.
View current Ann Arbor air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Ann Arbor, MI), 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.