St. Louis Air Quality in January
Across 2019–2025, St. Louis's January air quality had a median AQI of 56 (Moderate) over 217 monitored days in the St. Louis, MO-IL 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 2024 (median AQI 48, 0 days above 100) and the worst was 2020 (median 61, 0 days above 100, peak AQI 76).
- Good: 24.0%
- Moderate: 76.0%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
Extra Protection for St. Louis Homes
Air quality in St. Louis is moderate (AQI 60), with fine particles (PM2.5) the main concern. A True-HEPA purifier gives sensitive groups — kids, seniors and anyone with asthma or allergies — cleaner air indoors on days like today.
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How is the air in St. Louis in January?
Moderate on a typical day: median AQI 56 across 2019–2025, with 0.0% of January days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓24.0% of January days were Good (AQI 0–50), 76.0% Moderate (51–100).
- ✓0 days of 217 reached AQI 101+; the January peak was 89.
- ✓Best January: 2024; worst January: 2020.
Frequently asked questions
What is the air quality like in St. Louis in January?▾
Across 2019–2025, the median daily AQI in St. Louis in January was 56 (Moderate). 24.0% of days were Good, 76.0% 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 St. Louis?▾
A typical January day in St. Louis is Moderate (median AQI 56): 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 St. Louis's January air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 95.4% of January days in St. Louis. The highest January AQI recorded in 2019–2025 was 89 (Moderate), in 2020.
St. Louis January air quality, year by year
St. Louis January air quality by year (St. Louis, MO-IL, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 31 | 59 | 0 | 78 | PM2.5 |
| 2020worst | 31 | 61 | 0 | 76 | PM2.5 |
| 2021 | 31 | 58 | 0 | 89 | PM2.5 |
| 2022 | 31 | 57 | 0 | 88 | PM2.5 |
| 2023 | 31 | 59 | 0 | 81 | PM2.5 |
| 2024cleanest | 31 | 48 | 0 | 76 | PM2.5 |
| 2025 | 31 | 48 | 0 | 70 | PM2.5 |
What January air means in St. Louis
A typical January day in St. Louis is Moderate (median AQI 56): 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 56 is in line with St. Louis's whole-year median of 58, 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 St. Louis 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 St. Louis's winter season (December, January, February); the winter page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in St. Louis
The latest EPA AirNow observation puts St. Louis's AQI at 60 (PM2.5). The figures above are multi-year month statistics, not today's reading.
View current St. Louis air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (St. Louis, MO-IL), 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.