St. Paul Air Quality in Fall
Across 2019–2025, St. Paul's fall (September–November) air quality had a median AQI of 46 (Good) over 637 monitored days in the Minneapolis-St. Paul-Bloomington, MN-WI area. 0.2% of fall days (1 of 637) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 68.9% of days. The cleanest fall on record here was 2021 (median AQI 43, 0 days above 100) and the worst was 2024 (median 46, 1 day above 100, peak AQI 141).
- Good: 58.9%
- Moderate: 41.0%
- Unhealthy for Sensitive Groups: 0.2%
- Unhealthy or worse: 0.0%
Reduce Indoor Ozone in St. Paul
Today's main pollutant in St. Paul is ground-level ozone (AQI 25). Important: standard HEPA filters do NOT remove ozone — only a purifier with a substantial activated-carbon bed adsorbs it. The biggest wins are cutting indoor sources (gas appliances, certain "ionizer" purifiers) and ventilating when outdoor ozone is low (early morning). A high-carbon unit helps with the gases and VOCs that linger indoors.
Recommended: Levoit Core 300 — True HEPA + activated carbon · CADR ~141 CFM · rooms up to 219 sq ft
As an Amazon Associate, we earn from qualifying purchases.
How is the air in St. Paul in fall?
Good on a typical day: median AQI 46 across 2019–2025, with 0.2% of fall days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓58.9% of fall days were Good (AQI 0–50), 41.0% Moderate (51–100).
- ✓1 day of 637 reached AQI 101+; the fall peak was 141.
- ✓Cleanest month: October; worst month: September.
Frequently asked questions
What is the air quality like in St. Paul in fall?▾
Across 2019–2025, the median daily AQI in St. Paul in fall was 46 (Good). 58.9% of days were Good, 41.0% Moderate, and 0.2% reached Unhealthy for Sensitive Groups or worse, based on 637 monitored days in EPA's Air Quality System.
Is fall a good time for outdoor exercise in St. Paul?▾
A typical fall day in St. Paul sits in the Good range (median AQI 46), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of fall days reached AQI 101+ in 2019–2025.
Which pollutant causes St. Paul's fall air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 68.9% of fall days in St. Paul. The highest fall AQI recorded in 2019–2025 was 141 (Unhealthy for Sensitive Groups), in 2024.
St. Paul fall air quality, year by year
St. Paul fall air quality by year (Minneapolis-St. Paul-Bloomington, MN-WI, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 91 | 44 | 0 | 74 | PM2.5 |
| 2020 | 91 | 45 | 0 | 80 | PM2.5 |
| 2021cleanest | 91 | 43 | 0 | 88 | PM2.5 |
| 2022 | 91 | 52 | 0 | 91 | PM2.5 |
| 2023 | 91 | 46 | 0 | 90 | PM2.5 |
| 2024worst | 91 | 46 | 1 | 141 | PM2.5 |
| 2025 | 91 | 43 | 0 | 77 | PM2.5 |
What fall air means in St. Paul
A typical fall day in St. Paul sits in the Good range (median AQI 46), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of fall days reached AQI 101+ in 2019–2025.
Fall's median AQI of 46 is below St. Paul's whole-year median of 50, making it one of the area's cleaner periods. Nationally, the median Fall AQI across every EPA metro area (296,275 metro-days, 2019–2025) is 40, so St. Paul runs above the national Fall norm; 0.2% of its Fall days topped AQI 100 versus 1.5% nationally (below average).
Within the season, October is the cleanest month (median AQI 44, 0.0% of days above 100) and September the worst (median 48, 0.5% above 100).
Activity-specific thresholds: running, cycling, kids' sports.
Right now in St. Paul
The latest EPA AirNow observation puts St. Paul's AQI at 25 (O3). The figures above are multi-year season statistics, not today's reading.
View current St. Paul air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Minneapolis-St. Paul-Bloomington, MN-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.