St. Louis Air Quality in 2023
In 2023, St. Louis's air quality (St. Louis, MO-IL area) had a median daily AQI of 60 (Moderate) across 365 monitored days. 24 days (6.6%) reached Unhealthy for Sensitive Groups or worse, 51 were Good, and the year's peak AQI was 185 (Unhealthy). Fine particulate matter (PM2.5) set the daily AQI on 246 of those days. The cleanest month of 2023 was December (median AQI 53, 0 days above 100) and the worst was June (median 101, 15 days above 100, peak 185).
- Good: 14.0%
- Moderate: 79.5%
- Unhealthy for Sensitive Groups: 5.8%
- Unhealthy or worse: 0.8%
Improve Indoor Air Quality
Even with good outdoor air in St. Louis, indoor PM2.5, dust and allergens build up. A True-HEPA purifier keeps a bedroom or office consistently clean.
Recommended: Levoit Core 400S — True HEPA · CADR ~141 CFM · rooms up to 219 sq ft
As an Amazon Associate, we earn from qualifying purchases.
How was St. Louis's air quality in 2023?
Moderate on a typical day: median AQI 60, with 24 days above AQI 100 out of 365 monitored — the 7th cleanest of 7 years on record for the area.
- ✓Peak AQI in 2023: 185 (Unhealthy).
- ✓Fine particulate matter (PM2.5) was the main pollutant on 246 days.
- ✓Cleanest month: December; worst: June.
Frequently asked questions
What was the average AQI in St. Louis in 2023?▾
EPA's Air Quality System puts St. Louis's (St. Louis, MO-IL) median daily AQI for 2023 at 60, which is Moderate. 24 days were Unhealthy for Sensitive Groups or worse and the year's highest AQI was 185.
Which month had the worst air quality in St. Louis in 2023?▾
The cleanest month of 2023 was December (median AQI 53, 0 days above 100) and the worst was June (median 101, 15 days above 100, peak 185).
Was 2023 a good or bad year for St. Louis's air?▾
Among the 7 years EPA has published for the area (2019–2025), 2023 ranks 7th cleanest by days above AQI 100 — the worst year on record here. 2023's median of 60 is in line with the area's typical annual median of 58.
St. Louis month by month in 2023
St. Louis air quality month by month, 2023 (St. Louis, MO-IL, EPA AQS daily AQI)
| Month | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| January | 31 | 59 | 0 | 81 | PM2.5 |
| February | 28 | 58 | 0 | 84 | PM2.5 |
| March | 31 | 57 | 0 | 86 | PM2.5 |
| April | 30 | 59 | 1 | 103 | O3 |
| May | 31 | 74 | 6 | 147 | O3 |
| Juneworst | 30 | 101 | 15 | 185 | O3 |
| July | 31 | 74 | 1 | 105 | O3 |
| August | 31 | 56 | 0 | 93 | PM2.5 |
| September | 30 | 66 | 1 | 108 | PM2.5 |
| October | 31 | 54 | 0 | 99 | PM2.5 |
| November | 30 | 57 | 0 | 89 | PM2.5 |
| Decembercleanest | 31 | 53 | 0 | 69 | PM2.5 |
How 2023 compares
Among the 7 years EPA has published for the area (2019–2025), 2023 ranks 7th cleanest by days above AQI 100 — the worst year on record here.
2023's median of 60 is in line with the area's typical annual median of 58.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in St. Louis
The latest EPA AirNow observation puts St. Louis's AQI at 39 (PM2.5). The figures above are multi-year annual 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.