Cheyenne Air Quality in December
Across 2019–2025, Cheyenne's December air quality had a median AQI of 39 (Good) over 217 monitored days in the Cheyenne, WY area. 0.0% of December days (0 of 217) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 88.9% of days. The cleanest December on record here was 2019 (median AQI 36, 0 days above 100) and the worst was 2024 (median 42, 0 days above 100, peak AQI 47).
- Good: 97.2%
- Moderate: 2.8%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
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 December?
Good on a typical day: median AQI 39 across 2019–2025, with 0.0% of December days above AQI 100. Ground-level ozone is the main driver.
- ✓97.2% of December days were Good (AQI 0–50), 2.8% Moderate (51–100).
- ✓0 days of 217 reached AQI 101+; the December peak was 77.
- ✓Best December: 2019; worst December: 2024.
Frequently asked questions
What is the air quality like in Cheyenne in December?▾
Across 2019–2025, the median daily AQI in Cheyenne in December was 39 (Good). 97.2% of days were Good, 2.8% Moderate, and 0.0% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is December a good time for outdoor exercise in Cheyenne?▾
A typical December day in Cheyenne sits in the Good range (median AQI 39), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of December days reached AQI 101+ in 2019–2025.
Which pollutant causes Cheyenne's December air quality problems?▾
Ground-level ozone set the daily AQI on 88.9% of December days in Cheyenne. The highest December AQI recorded in 2019–2025 was 77 (Moderate), in 2024.
Cheyenne December air quality, year by year
Cheyenne December air quality by year (Cheyenne, WY, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019cleanest | 31 | 36 | 0 | 44 | O3 |
| 2020 | 31 | 37 | 0 | 46 | O3 |
| 2021 | 31 | 39 | 0 | 77 | O3 |
| 2022 | 31 | 37 | 0 | 42 | O3 |
| 2023 | 31 | 40 | 0 | 60 | O3 |
| 2024worst | 31 | 42 | 0 | 47 | O3 |
| 2025 | 31 | 39 | 0 | 44 | O3 |
What December air means in Cheyenne
A typical December day in Cheyenne sits in the Good range (median AQI 39), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of December days reached AQI 101+ in 2019–2025.
December's median AQI of 39 is below Cheyenne's whole-year median of 44, making it one of the area's cleaner periods. Nationally, the median December AQI across every EPA metro area (95,590 metro-days, 2019–2025) is 39, so Cheyenne runs in line with the national December norm; 0.0% of its December days topped AQI 100 versus 0.7% nationally (about the same).
December is part of Cheyenne's winter season (December, January, February); the winter page pools all three months.
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 month 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.