Chicago Air Quality in January
Across 2019–2025, Chicago's January air quality had a median AQI of 57 (Moderate) over 217 monitored days in the Chicago-Naperville-Elgin, IL-IN-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 95.4% of days. The cleanest January on record here was 2025 (median AQI 54, 0 days above 100) and the worst was 2021 (median 61, 0 days above 100, peak AQI 87).
- Good: 18.9%
- Moderate: 81.1%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
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How is the air in Chicago in January?
Moderate on a typical day: median AQI 57 across 2019–2025, with 0.0% of January days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓18.9% of January days were Good (AQI 0–50), 81.1% Moderate (51–100).
- ✓0 days of 217 reached AQI 101+; the January peak was 96.
- ✓Best January: 2025; worst January: 2021.
Frequently asked questions
What is the air quality like in Chicago in January?▾
Across 2019–2025, the median daily AQI in Chicago in January was 57 (Moderate). 18.9% of days were Good, 81.1% 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 Chicago?▾
A typical January day in Chicago is Moderate (median AQI 57): 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 Chicago's January air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 95.4% of January days in Chicago. The highest January AQI recorded in 2019–2025 was 96 (Moderate), in 2021.
Chicago January air quality, year by year
Chicago January air quality by year (Chicago-Naperville-Elgin, IL-IN-WI, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 31 | 58 | 0 | 74 | PM2.5 |
| 2020 | 31 | 58 | 0 | 80 | PM2.5 |
| 2021worst | 31 | 61 | 0 | 87 | PM2.5 |
| 2022 | 31 | 57 | 0 | 96 | PM2.5 |
| 2023 | 31 | 58 | 0 | 84 | PM2.5 |
| 2024 | 31 | 56 | 0 | 81 | PM2.5 |
| 2025cleanest | 31 | 54 | 0 | 79 | PM2.5 |
What January air means in Chicago
A typical January day in Chicago is Moderate (median AQI 57): 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 57 is in line with Chicago's whole-year median of 60, 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 Chicago 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 Chicago's winter season (December, January, February); the winter page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Chicago
The latest EPA AirNow observation puts Chicago's AQI at 46 (PM2.5). The figures above are multi-year month statistics, not today's reading.
View current Chicago air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Chicago-Naperville-Elgin, IL-IN-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.