Cheyenne Air Quality in Fall
Across 2019–2025, Cheyenne's fall (September–November) air quality had a median AQI of 42 (Good) over 637 monitored days in the Cheyenne, WY area. 0.8% of fall days (5 of 637) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 82.1% of days. The cleanest fall on record here was 2022 (median AQI 39, 0 days above 100) and the worst was 2020 (median 41, 5 days above 100, peak AQI 159).
- Good: 82.7%
- Moderate: 16.5%
- Unhealthy for Sensitive Groups: 0.5%
- Unhealthy or worse: 0.3%
Reduce Indoor Ozone in Cheyenne
Today's main pollutant in Cheyenne is ground-level ozone (AQI 31). 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
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How is the air in Cheyenne in fall?
Good on a typical day: median AQI 42 across 2019–2025, with 0.8% of fall days above AQI 100. Ground-level ozone is the main driver.
- ✓82.7% of fall days were Good (AQI 0–50), 16.5% Moderate (51–100).
- ✓5 days of 637 reached AQI 101+; the fall peak was 159.
- ✓Cleanest month: November; worst month: October.
Frequently asked questions
What is the air quality like in Cheyenne in fall?▾
Across 2019–2025, the median daily AQI in Cheyenne in fall was 42 (Good). 82.7% of days were Good, 16.5% Moderate, and 0.8% 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 Cheyenne?▾
A typical fall day in Cheyenne sits in the Good range (median AQI 42), 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 Cheyenne's fall air quality problems?▾
Ground-level ozone set the daily AQI on 82.1% of fall days in Cheyenne. The highest fall AQI recorded in 2019–2025 was 159 (Unhealthy), in 2020.
Cheyenne fall air quality, year by year
Cheyenne fall air quality by year (Cheyenne, WY, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 91 | 41 | 0 | 71 | O3 |
| 2020worst | 91 | 41 | 5 | 159 | O3 |
| 2021 | 91 | 42 | 0 | 84 | O3 |
| 2022cleanest | 91 | 39 | 0 | 77 | O3 |
| 2023 | 91 | 43 | 0 | 62 | O3 |
| 2024 | 91 | 44 | 0 | 67 | O3 |
| 2025 | 91 | 43 | 0 | 90 | O3 |
What fall air means in Cheyenne
A typical fall day in Cheyenne sits in the Good range (median AQI 42), 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 42 is in line with Cheyenne's whole-year median of 44, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median Fall AQI across every EPA metro area (296,275 metro-days, 2019–2025) is 40, so Cheyenne runs in line with the national Fall norm; 0.8% of its Fall days topped AQI 100 versus 1.5% nationally (about the same).
Within the season, November is the cleanest month (median AQI 39, 0.0% of days above 100) and October the worst (median 41, 1.9% above 100).
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Cheyenne
The latest EPA AirNow observation puts Cheyenne's AQI at 31 (O3). The figures above are multi-year season statistics, not today's reading.
View current Cheyenne air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Cheyenne, WY), 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.