Denver Air Quality in 2023
In 2023, Denver's air quality (Denver-Aurora-Lakewood, CO area) had a median daily AQI of 64 (Moderate) across 365 monitored days. 29 days (7.9%) reached Unhealthy for Sensitive Groups or worse, 72 were Good, and the year's peak AQI was 179 (Unhealthy). Ground-level ozone set the daily AQI on 243 of those days. The cleanest month of 2023 was October (median AQI 52, 0 days above 100) and the worst was July (median 90, 8 days above 100, peak 115).
- Good: 19.7%
- Moderate: 72.3%
- Unhealthy for Sensitive Groups: 7.4%
- Unhealthy or worse: 0.5%
Reduce Indoor Ozone in Denver
Today's main pollutant in Denver is ground-level ozone (AQI 48). 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 was Denver's air quality in 2023?
Moderate on a typical day: median AQI 64, with 29 days above AQI 100 out of 365 monitored — the 3rd cleanest of 7 years on record for the area.
- ✓Peak AQI in 2023: 179 (Unhealthy).
- ✓Ground-level ozone was the main pollutant on 243 days.
- ✓Cleanest month: October; worst: July.
Frequently asked questions
What was the average AQI in Denver in 2023?▾
EPA's Air Quality System puts Denver's (Denver-Aurora-Lakewood, CO) median daily AQI for 2023 at 64, which is Moderate. 29 days were Unhealthy for Sensitive Groups or worse and the year's highest AQI was 179.
Which month had the worst air quality in Denver in 2023?▾
The cleanest month of 2023 was October (median AQI 52, 0 days above 100) and the worst was July (median 90, 8 days above 100, peak 115).
Was 2023 a good or bad year for Denver's air?▾
Among the 7 years EPA has published for the area (2019–2025), 2023 ranks 3rd cleanest by days above AQI 100. 2023's median of 64 is in line with the area's typical annual median of 64.
Denver month by month in 2023
Denver air quality month by month, 2023 (Denver-Aurora-Lakewood, CO, EPA AQS daily AQI)
| Month | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| January | 31 | 58 | 0 | 89 | PM2.5 |
| February | 28 | 54 | 0 | 76 | O3 |
| March | 31 | 59 | 0 | 77 | O3 |
| April | 30 | 76 | 3 | 147 | O3 |
| May | 31 | 80 | 4 | 179 | O3 |
| June | 30 | 84 | 5 | 126 | O3 |
| Julyworst | 31 | 90 | 8 | 115 | O3 |
| August | 31 | 84 | 8 | 143 | O3 |
| September | 30 | 71 | 1 | 122 | O3 |
| Octobercleanest | 31 | 52 | 0 | 78 | O3 |
| November | 30 | 56 | 0 | 67 | O3 |
| December | 31 | 52 | 0 | 88 | PM2.5 |
How 2023 compares
Among the 7 years EPA has published for the area (2019–2025), 2023 ranks 3rd cleanest by days above AQI 100.
2023's median of 64 is in line with the area's typical annual median of 64.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Denver
The latest EPA AirNow observation puts Denver's AQI at 48 (O3). The figures above are multi-year annual statistics, not today's reading.
View current Denver 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.