Aurora, CO Air Quality in December
Across 2019–2025, Aurora's December air quality had a median AQI of 52 (Moderate) over 217 monitored days in the Denver-Aurora-Lakewood, CO area. 0.0% of December days (0 of 217) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 38.2% of days. The cleanest December on record here was 2025 (median AQI 48, 0 days above 100) and the worst was 2019 (median 61, 0 days above 100, peak AQI 83).
- Good: 40.1%
- Moderate: 59.9%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
Reduce Indoor Ozone in Aurora
Today's main pollutant in Aurora is ground-level ozone (AQI 39). 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.
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How is the air in Aurora in December?
Moderate on a typical day: median AQI 52 across 2019–2025, with 0.0% of December days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓40.1% of December days were Good (AQI 0–50), 59.9% Moderate (51–100).
- ✓0 days of 217 reached AQI 101+; the December peak was 93.
- ✓Best December: 2025; worst December: 2019.
Frequently asked questions
What is the air quality like in Aurora in December?▾
Across 2019–2025, the median daily AQI in Aurora in December was 52 (Moderate). 40.1% of days were Good, 59.9% 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 Aurora?▾
A typical December day in Aurora is Moderate (median AQI 52): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and fewer than 1% of December days reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Which pollutant causes Aurora's December air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 38.2% of December days in Aurora. The highest December AQI recorded in 2019–2025 was 93 (Moderate), in 2019.
Aurora December air quality, year by year
Aurora December air quality by year (Denver-Aurora-Lakewood, CO, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019worst | 31 | 61 | 0 | 83 | PM2.5 |
| 2020 | 31 | 53 | 0 | 93 | PM2.5 |
| 2021 | 31 | 51 | 0 | 78 | NO2 |
| 2022 | 31 | 56 | 0 | 77 | PM2.5 |
| 2023 | 31 | 52 | 0 | 88 | PM2.5 |
| 2024 | 31 | 51 | 0 | 93 | O3 |
| 2025cleanest | 31 | 48 | 0 | 64 | O3 |
What December air means in Aurora
A typical December day in Aurora is Moderate (median AQI 52): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and fewer than 1% of December days reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
December's median AQI of 52 is below Aurora's whole-year median of 64, 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 Aurora runs above the national December norm; 0.0% of its December days topped AQI 100 versus 0.7% nationally (about the same).
December is part of Aurora's winter season (December, January, February); the winter page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Aurora
The latest EPA AirNow observation puts Aurora's AQI at 39 (O3). The figures above are multi-year month statistics, not today's reading.
View current Aurora air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Denver-Aurora-Lakewood, CO), 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.