Median AQI
19
Good
Colorado · County air quality · 2025
Pitkin County, Colorado
Median AQI 19 (Good). 92.3% of monitored days rated Good, direct from EPA Air Quality System stations.
- 19
- Median AQI
- 92.3%
- Good-air days
- 1
- Unhealthy days
- 85%
- Cleaner than US counties
Pitkin County's 2025 annual median AQI is 19 (Good), with 92.3% Good days
According to the U.S. EPA Air Quality System, Pitkin County, Colorado posted a 2025 median AQI of 19 (Good) across 365 monitored days, with 92.3% rated Good and 1 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Pitkin County's 92.3% Good-day share places it cleaner than 85% of US counties in 2025.
- Closest median-AQI peer
- Cass County (95.9% Good, median AQI 19) is the closest nationwide median-AQI peer to Pitkin County.
- 2020–2025 trend
- Pitkin County's floor-qualifying Good-day share is worsening from 2020 to 2025 (96.7% → 92.3%).
- Median AQI
- Median AQI: 19
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 19 with 92.3% of 365 monitored days in the Good band, driven mainly by PM2.5.
- 19
- median AQI · Good
- 92.3%
- days rated Good
- PM2.5
- main pollutant
- 85%
- cleaner than US counties
1 day reached Unhealthy or worse; the worst single reading hit AQI 154.
Annual release change
What changed in the 2025 EPA annual release
- Pitkin County's peak single-day AQI rose from 76 to 154 between the 2024 and 2025 EPA annual releases, a change of +78 points.
- Pitkin County's Good-day share fell from 95.7% to 92.3% between the 2024 and 2025 EPA annual releases, a change of -3.4 percentage points.
- Pitkin County's Unhealthy-category days rose from 0 to 1 between the 2024 and 2025 EPA annual releases, a change of +1 days.
Data updated August 2026
- Good · 337 d · 92.3%
- Moderate · 27 d · 7.4%
- Unhealthy · 1 d · 0.3%
How did Pitkin County's air break down in 2025?
Across 365 monitored days, 337 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). 365 days monitored. Median AQI: 19 (Good).
Insights: Pitkin County, Colorado. EPA monitors recorded a median Air Quality Index of 19 across 365 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 337 (92%) fell in the Good band (AQI 0–50), 27 (7%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 43, while the worst single-day peak hit 154 (Unhealthy). Residents averaged about 27.7 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (305 days), PM10 (60 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by -4.3 points (measured against 120 monitored days in 2020 and 365 in 2025, so raw day counts are not comparable) and the median AQI moved +7 points, placing the multi-year trajectory at worsening. The annual record contains 1 day at Unhealthy or worse. On that day, the EPA recommends that sensitive groups limit prolonged outdoor exertion. Nearby counties show comparable readings: Adams (55.1% good, AQI 49); Alamosa (91.5% good, AQI 25); Arapahoe (58.1% good, AQI 48); Archuleta (83.0% good, AQI 34); Boulder (58.4% good, AQI 48); Chaffee (66.0% good, AQI 48).
Air Quality Summary
Good Days
92.3%
337 of 365 monitored days
17.3pp vs 75% target
Max AQI Recorded
154
Unhealthy
Health Grade
Excellent
90th-pct AQI 43
Pitkin County, Good days share 92.3%
National avg
Share of monitored days at AQI 0-50 (Good band).
Pitkin County, Unhealthy-or-worse share 2.7%
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 365 monitored days across EPA AQI categories.
Good
337
92%
Moderate
27
7%
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 · 305 days · 83.6%
- PM10 · 60 days · 16.4%
Health Impact Assessment
Excellent
Pitkin County's air quality is rated Excellent based on 92.3% 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 305 of 365 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Pitkin County. Highest Good-day share: 2023 (99.2%, 120 of 121 monitored 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 | 337 | 27 | 0 | 1 | 19 | 154 |
How does Pitkin County compare?
How Pitkin County compares
Good-day share better than typical
Pitkin County 92.3%
Cass County, Nebraska 95.9%
Typical US county 76.0%
Median AQI better than typical
Pitkin County 19
Cass County, Nebraska 19
Typical US county 39
Unhealthy days / yr about typical
Pitkin County 1
Cass County, Nebraska 0
Typical US county 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Pitkin County (19), not geographic neighbors.
Cass County, Nebraska
Median AQI 19 · 95.9% Good-day share
Garfield County, Washington
Median AQI 19 · 92.5% Good-day share
Marquette County, Michigan
Median AQI 19 · 82.4% Good-day share
Phillips County, Montana
Median AQI 19 · 91.4% Good-day share
Dawson County, Montana
Median AQI 18 · 90.3% Good-day share
Hughes County, South Dakota
Median AQI 18 · 93.0% Good-day share
Same primary pollutant: PM2.5
PM2.5 led the AQI on the most monitored days here. These peers share that driver and the closest Good-day share (a second relationship type beyond median-AQI neighbors).
Hill County, Montana
92.1% Good-day share · median AQI 14
Prowers County, Colorado
92.6% Good-day share · median AQI 27
Windham County, Vermont
92.0% Good-day share · median AQI 15
Columbia County, Oregon
92.9% Good-day share · median AQI 27
Twin Falls County, Idaho
92.9% Good-day share · median AQI 26
Lubbock County, Texas
92.9% Good-day share · median AQI 24
Colorado counties on the map
Geographic containment only, other monitored counties in Colorado, independent of AQI or pollutant match.
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 19 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 365 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
Keep exploring the annual AQI record
Air-quality reading list
Frequently Asked Questions
What is the air quality in Pitkin County, Colorado? ▼
Pitkin County has a median Air Quality Index (AQI) of 19, rated "Good." 92.3% of monitored days (337 out of 365) 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 305 days (84% 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 across floor-qualifying years (2020-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2023 at 99.2% (120 of 121 days). Lowest qualifying Good-day share: 2025 at 92.3% (337 of 365 days).
What does AQI 19 mean for health? ▼
Pitkin County's median AQI of 19 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does Pitkin County compare to other counties in Colorado? ▼
Pitkin County has 92.3% good air days. Nearby counties in Colorado: Adams (55.1% good), Alamosa (91.5% good), Arapahoe (58.1% good), Archuleta (83.0% good), Boulder (58.4% good), Chaffee (66.0% good).
What is the 90th percentile AQI in Pitkin County? ▼
The 90th percentile AQI for Pitkin County is 43, 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. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Pitkin County, Colorado · 2020–2025
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Every figure on PlainAirData 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.