Denver Air Quality in Spring
Across 2019–2025, Denver's spring (March–May) air quality had a median AQI of 64 (Moderate) over 644 monitored days in the Denver-Aurora-Lakewood, CO area. 4.2% of spring days (27 of 644) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 81.1% of days. The cleanest spring on record here was 2020 (median AQI 61, 1 day above 100) and the worst was 2023 (median 67, 7 days above 100, peak AQI 179).
- Good: 17.4%
- Moderate: 78.4%
- Unhealthy for Sensitive Groups: 3.4%
- Unhealthy or worse: 0.8%
Reduce Indoor Ozone in Denver
Today's main pollutant in Denver is ground-level ozone (AQI 43). 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 Denver in spring?
Moderate on a typical day: median AQI 64 across 2019–2025, with 4.2% of spring days above AQI 100. Ground-level ozone is the main driver.
- ✓17.4% of spring days were Good (AQI 0–50), 78.4% Moderate (51–100).
- ✓27 days of 644 reached AQI 101+; the spring peak was 190.
- ✓Cleanest month: March; worst month: May.
Frequently asked questions
What is the air quality like in Denver in spring?▾
Across 2019–2025, the median daily AQI in Denver in spring was 64 (Moderate). 17.4% of days were Good, 78.4% Moderate, and 4.2% reached Unhealthy for Sensitive Groups or worse, based on 644 monitored days in EPA's Air Quality System.
Is spring a good time for outdoor exercise in Denver?▾
A typical spring day in Denver is Moderate (median AQI 64): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 24 of spring days (4.2%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Which pollutant causes Denver's spring air quality problems?▾
Ground-level ozone set the daily AQI on 81.1% of spring days in Denver. The highest spring AQI recorded in 2019–2025 was 190 (Unhealthy), in 2023.
Denver spring air quality, year by year
Denver spring air quality by year (Denver-Aurora-Lakewood, CO, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 92 | 67 | 3 | 153 | O3 |
| 2020cleanest | 92 | 61 | 1 | 105 | O3 |
| 2021 | 92 | 61 | 3 | 151 | O3 |
| 2022 | 92 | 60 | 2 | 190 | O3 |
| 2023worst | 92 | 67 | 7 | 179 | O3 |
| 2024 | 92 | 71 | 6 | 133 | O3 |
| 2025 | 92 | 63 | 5 | 115 | O3 |
What spring air means in Denver
A typical spring day in Denver is Moderate (median AQI 64): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 24 of spring days (4.2%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Spring's median AQI of 64 is in line with Denver's whole-year median of 64, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median Spring AQI across every EPA metro area (307,196 metro-days, 2019–2025) is 43, so Denver runs above the national Spring norm; 4.2% of its Spring days topped AQI 100 versus 0.8% nationally (above average).
Within the season, March is the cleanest month (median AQI 58, 1.9% of days above 100) and May the worst (median 74, 7.4% above 100).
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Denver
The latest EPA AirNow observation puts Denver's AQI at 43 (O3). The figures above are multi-year season 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.