Fort Collins Air Quality in Summer
Across 2019–2025, Fort Collins's summer (June–August) air quality had a median AQI of 69 (Moderate) over 644 monitored days in the Fort Collins, CO area. 13.8% of summer days (89 of 644) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 95.7% of days. The cleanest summer on record here was 2023 (median AQI 61, 3 days above 100) and the worst was 2021 (median 93, 36 days above 100, peak AQI 159).
- Good: 20.7%
- Moderate: 65.5%
- Unhealthy for Sensitive Groups: 12.9%
- Unhealthy or worse: 0.9%
Reduce Indoor Ozone in Fort Collins
Today's main pollutant in Fort Collins is ground-level ozone (AQI 36). 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 Fort Collins in summer?
Moderate on a typical day: median AQI 69 across 2019–2025, with 13.8% of summer days above AQI 100. Ground-level ozone is the main driver.
- ✓20.7% of summer days were Good (AQI 0–50), 65.5% Moderate (51–100).
- ✓89 days of 644 reached AQI 101+; the summer peak was 161.
- ✓Cleanest month: June; worst month: July.
Frequently asked questions
What is the air quality like in Fort Collins in summer?▾
Across 2019–2025, the median daily AQI in Fort Collins in summer was 69 (Moderate). 20.7% of days were Good, 65.5% Moderate, and 13.8% reached Unhealthy for Sensitive Groups or worse, based on 644 monitored days in EPA's Air Quality System.
Is summer a good time for outdoor exercise in Fort Collins?▾
A typical summer day in Fort Collins is Moderate (median AQI 69): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 7 of summer days (13.8%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Which pollutant causes Fort Collins's summer air quality problems?▾
Ground-level ozone set the daily AQI on 95.7% of summer days in Fort Collins. The highest summer AQI recorded in 2019–2025 was 161 (Unhealthy), in 2021.
Fort Collins summer air quality, year by year
Fort Collins summer air quality by year (Fort Collins, CO, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 92 | 63 | 4 | 129 | O3 |
| 2020 | 92 | 69 | 9 | 146 | O3 |
| 2021worst | 92 | 93 | 36 | 159 | O3 |
| 2022 | 92 | 69 | 7 | 126 | O3 |
| 2023cleanest | 92 | 61 | 3 | 156 | O3 |
| 2024 | 92 | 74 | 23 | 161 | O3 |
| 2025 | 92 | 64 | 7 | 119 | O3 |
What summer air means in Fort Collins
A typical summer day in Fort Collins is Moderate (median AQI 69): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 7 of summer days (13.8%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Summer's median AQI of 69 is above Fort Collins's whole-year median of 51, making it one of the area's dirtier periods. Nationally, the median Summer AQI across every EPA metro area (308,645 metro-days, 2019–2025) is 46, so Fort Collins runs above the national Summer norm; 13.8% of its Summer days topped AQI 100 versus 3.6% nationally (above average).
Within the season, June is the cleanest month (median AQI 64, 9.1% of days above 100) and July the worst (median 74, 17.9% above 100).
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Fort Collins
The latest EPA AirNow observation puts Fort Collins's AQI at 36 (O3). The figures above are multi-year season statistics, not today's reading.
View current Fort Collins air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Fort Collins, 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.