Median AQI
21
Good
Colorado · County air quality · 2025
Pitkin County, Colorado
Median AQI 21 (Good). 91.6% of monitored days rated Good, direct from EPA Air Quality System stations.
- 21
- Median AQI
- 91.6%
- Good-air days
- 1
- Unhealthy days
- 79%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Pitkin County's air is good on balance, cleaner than most US counties, a median AQI of 21 with 91.6% of 273 monitored days in the Good band, driven mainly by PM2.5.
- 21
- median AQI · Good
- 91.6%
- days rated Good
- PM2.5
- main pollutant
- 79%
- cleaner than US counties
1 day reached Unhealthy or worse; the worst single reading hit AQI 154.
Data updated July 2026
- Good · 250 d · 91.6%
- Moderate · 22 d · 8.1%
- Unhealthy · 1 d · 0.4%
How did Pitkin County's air break down in 2025?
Across 273 monitored days, 250 fell in the Good band (AQI 0–50) and 1 reached Unhealthy or worse. The worst single day peaked at AQI 154 (Unhealthy).
EPA AQS →Air quality data from EPA Air Quality System (2025). 273 days monitored. Median AQI: 21 (Good).
Insights: Pitkin County, Colorado. EPA monitors recorded a median Air Quality Index of 21 across 273 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 250 (92%) fell in the Good band (AQI 0–50), 22 (8%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 45, while the worst single-day peak hit 154 (Unhealthy). Residents averaged about 27.5 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (234 days), PM10 (39 days). Across the 2020–2025 trend window, good days shifted by +134 and the median AQI moved +9 points, placing the multi-year trajectory at worsening. Residents and visitors experienced 1 unhealthy-or-worse days combined, periods when the EPA recommends sensitive groups limit prolonged outdoor exertion. Nearby counties show comparable readings: Adams (50.2% good, AQI 50); Alamosa (90.8% good, AQI 24); Arapahoe (47.3% good, AQI 51); Archuleta (79.5% good, AQI 32); Boulder (50.9% good, AQI 50); Clear Creek (64.4% good, AQI 48).
Air Quality Summary
Good Days
91.6%
250 of 273 monitored days
16.6pp vs 75% target
Max AQI Recorded
154
Unhealthy
Health Grade
Excellent
90th-pct AQI 45
Pitkin County, Good days share 91.6%
National avg
Share of monitored days at AQI 0-50 (Good band).
Pitkin County, Unhealthy-or-worse share 0.4%
National avg
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
AQI Day Breakdown (2025)
Distribution of 273 monitored days across EPA AQI categories.
Good
250
92%
Moderate
22
8%
USG
0
0%
Unhealthy
1
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Pitkin County.
- PM2.5 · 234 days · 85.7%
- PM10 · 39 days · 14.3%
Health Impact Assessment
Excellent
Pitkin County's air quality is rated Excellent based on 91.6% good air days. There were 1 unhealthy days in 2025 when outdoor activity should be limited.
Air quality is acceptable most days, but 0 days reached "Unhealthy for Sensitive Groups" (AQI 101-150) and peak AQI reached 154. Sensitive groups should monitor real-time conditions at AirNow.gov.
The dominant pollutant is PM2.5, driving AQI on 234 of 273 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Pitkin County. Best year: 2025 (250 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 116 | 4 | 0 | 0 | 12 | 72 |
| 2021 | 115 | 7 | 0 | 0 | 14 | 90 |
| 2022 | 118 | 4 | 0 | 0 | 14 | 72 |
| 2023 | 120 | 1 | 0 | 0 | 13 | 51 |
| 2024 | 246 | 11 | 0 | 0 | 19 | 76 |
| 2025 | 250 | 22 | 0 | 1 | 21 | 154 |
How does Pitkin County compare?
How Pitkin County compares
Good-day share better than US avg
Pitkin County 91.6%
Adams County, Colorado 50.2%
US average 76.5%
Median AQI better than US avg
Pitkin County 21
Adams County, Colorado 50
US average 38
Unhealthy days / yr worse than US avg
Pitkin County 1
Adams County, Colorado 0
US average 0
Other Counties in Colorado
Air quality comparison for nearby counties in Colorado.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Pitkin County.
Cowlitz County, Washington
AQI 21 · 91.6% good
Juneau County, Alaska
AQI 21 · 85.1% good
Kitsap County, Washington
AQI 21 · 96.2% good
Marin County, California
AQI 21 · 100.0% good
Mason County, Washington
AQI 21 · 92.6% good
Putnam County, Florida
AQI 21 · 96.0% good
What Pitkin County's air means for you
On most days the air here is fine, but PM2.5 drives 1 unhealthy-or-worse day a year that sensitive groups should plan around.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM2.5 days, the guide explains what a median of 21 means for exposure. Health guidance
- See how Pitkin County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Pitkin County with its Colorado neighbours before drawing a conclusion about the region. All of Colorado
Based on 273 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
More Air Quality Data
Air Quality Guides
Frequently Asked Questions
What is the air quality in Pitkin County, Colorado? ▼
Pitkin County has a median Air Quality Index (AQI) of 21, rated "Good." 91.6% of monitored days (250 out of 273) had good air quality in 2025.
What is the main pollutant in Pitkin County? ▼
The primary pollutant in Pitkin County is Fine Particles (PM2.5), which was the main AQI driver on 234 days (86% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Pitkin County have? ▼
In 2025, Pitkin County recorded 1 unhealthy air days (1 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 154.
Is the air quality in Pitkin County getting better or worse? ▼
Air quality in Pitkin County is worsening based on 5-year trends (2020-2025). Best year: 2025 with 250 good days. Worst year: 2021 with 115 good days.
What does AQI 21 mean for health? ▼
Pitkin County's median AQI of 21 falls in the "Good" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Pitkin County compare to other counties in Colorado? ▼
Pitkin County has 91.6% good air days. Nearby counties in Colorado: Adams (50.2% good), Alamosa (90.8% good), Arapahoe (47.3% good), Archuleta (79.5% good), Boulder (50.9% good), Clear Creek (64.4% good).
What is the 90th percentile AQI in Pitkin County? ▼
The 90th percentile AQI for Pitkin County is 45, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 154 (Unhealthy).
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer.
Every figure on PlainAir is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.