St. Louis Air Quality in July
Across 2019–2025, St. Louis's July air quality had a median AQI of 63 (Moderate) over 217 monitored days in the St. Louis, MO-IL area. 9.2% of July days (20 of 217) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 52.5% of days. The cleanest July on record here was 2025 (median AQI 57, 1 day above 100) and the worst was 2021 (median 66, 6 days above 100, peak AQI 187).
- Good: 12.4%
- Moderate: 78.3%
- Unhealthy for Sensitive Groups: 7.4%
- Unhealthy or worse: 1.8%
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 is the air in St. Louis in July?
Moderate on a typical day: median AQI 63 across 2019–2025, with 9.2% of July days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓12.4% of July days were Good (AQI 0–50), 78.3% Moderate (51–100).
- ✓20 days of 217 reached AQI 101+; the July peak was 187.
- ✓Best July: 2025; worst July: 2021.
Frequently asked questions
What is the air quality like in St. Louis in July?▾
Across 2019–2025, the median daily AQI in St. Louis in July was 63 (Moderate). 12.4% of days were Good, 78.3% Moderate, and 9.2% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is July a good time for outdoor exercise in St. Louis?▾
A typical July day in St. Louis is Moderate (median AQI 63): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 11 of July days (9.2%) 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 July air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 52.5% of July days in St. Louis. The highest July AQI recorded in 2019–2025 was 187 (Unhealthy), in 2021.
St. Louis July air quality, year by year
St. Louis July 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 | 67 | 3 | 151 | O3 |
| 2020 | 31 | 61 | 4 | 156 | O3 |
| 2021worst | 31 | 66 | 6 | 187 | PM2.5 |
| 2022 | 31 | 64 | 3 | 140 | O3 |
| 2023 | 31 | 74 | 1 | 105 | O3 |
| 2024 | 31 | 59 | 2 | 109 | PM2.5 |
| 2025cleanest | 31 | 57 | 1 | 101 | PM2.5 |
What July air means in St. Louis
A typical July day in St. Louis is Moderate (median AQI 63): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 11 of July days (9.2%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
July's median AQI of 63 is above St. Louis's whole-year median of 58, making it one of the area's dirtier periods. Nationally, the median July AQI across every EPA metro area (103,858 metro-days, 2019–2025) is 47, so St. Louis runs above the national July norm; 9.2% of its July days topped AQI 100 versus 3.6% nationally (above average).
July is part of St. Louis's summer season (June, July, August); the summer 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.