St. Louis Air Quality in 2024
In 2024, St. Louis's air quality (St. Louis, MO-IL area) had a median daily AQI of 55 (Moderate) across 366 monitored days. 16 days (4.4%) reached Unhealthy for Sensitive Groups or worse, 117 were Good, and the year's peak AQI was 165 (Unhealthy). Fine particulate matter (PM2.5) set the daily AQI on 228 of those days. The cleanest month of 2024 was November (median AQI 44, 0 days above 100) and the worst was September (median 52, 3 days above 100, peak 119).
- Good: 32.0%
- Moderate: 63.7%
- Unhealthy for Sensitive Groups: 3.6%
- Unhealthy or worse: 0.8%
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.
Recommended: Coway AP-1512HH Mighty — True HEPA + carbon · CADR ~246 CFM · rooms up to 361 sq ft
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How was St. Louis's air quality in 2024?
Moderate on a typical day: median AQI 55, with 16 days above AQI 100 out of 366 monitored — the 6th cleanest of 7 years on record for the area.
- ✓Peak AQI in 2024: 165 (Unhealthy).
- ✓Fine particulate matter (PM2.5) was the main pollutant on 228 days.
- ✓Cleanest month: November; worst: September.
Frequently asked questions
What was the average AQI in St. Louis in 2024?▾
EPA's Air Quality System puts St. Louis's (St. Louis, MO-IL) median daily AQI for 2024 at 55, which is Moderate. 16 days were Unhealthy for Sensitive Groups or worse and the year's highest AQI was 165.
Which month had the worst air quality in St. Louis in 2024?▾
The cleanest month of 2024 was November (median AQI 44, 0 days above 100) and the worst was September (median 52, 3 days above 100, peak 119).
Was 2024 a good or bad year for St. Louis's air?▾
Among the 7 years EPA has published for the area (2019–2025), 2024 ranks 6th cleanest by days above AQI 100. 2024's median of 55 is below the area's typical annual median of 58.
St. Louis month by month in 2024
St. Louis air quality month by month, 2024 (St. Louis, MO-IL, EPA AQS daily AQI)
| Month | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| January | 31 | 48 | 0 | 76 | PM2.5 |
| February | 29 | 59 | 2 | 156 | PM2.5 |
| March | 31 | 56 | 0 | 81 | PM2.5 |
| April | 30 | 54 | 1 | 133 | O3 |
| May | 31 | 55 | 1 | 142 | O3 |
| June | 30 | 66 | 2 | 165 | O3 |
| July | 31 | 59 | 2 | 109 | PM2.5 |
| August | 31 | 58 | 2 | 151 | PM2.5 |
| Septemberworst | 30 | 52 | 3 | 119 | O3 |
| October | 31 | 71 | 3 | 131 | PM10 |
| Novembercleanest | 30 | 44 | 0 | 58 | PM2.5 |
| December | 31 | 49 | 0 | 69 | PM2.5 |
How 2024 compares
Among the 7 years EPA has published for the area (2019–2025), 2024 ranks 6th cleanest by days above AQI 100.
2024's median of 55 is below 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 60 (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.