Counties Tracked
977
EPA AQS active monitors
EPA Air Quality System · 977 counties · 2020-2025
How clean is the air
where you live?
AQI summaries, pollutant breakdowns, and good-day trends for 977 U.S. counties, 496 metros, and 53 states, direct from EPA AQS.
- Counties monitored
- 977
- Metro areas
- 496
- States covered
- 53
- Years of data
- 2020-2025
- Good · 2,272 d · 100.0%
- Moderate · 1 d · 0.0%
The national picture
Across 977 monitored U.S. counties, the typical day lands at AQI 39 - inside the Good band, but the most-polluted 10% of counties average AQI 54, 3.7x higher than the cleanest 10% at AQI 15, yet only 77% of monitored days clear the Good threshold nationwide.
- 39
- national median AQI (Good, 0–50)
- 76.5%
- of monitored days rated Good
- 3.7x
- dirtiest-decile vs cleanest-decile AQI gap
- 977
- counties with an active EPA monitor
Cleanest typical air sits in Karnes, Texas; the heaviest chronic load falls on San Bernardino, California.
Metro Areas
496
MSA-level aggregation
Avg Median AQI
38.5
Good
Avg Good Days
76.5%
Share of monitored days at AQI ≤50
6.5pp vs 70% benchmark
According to the U.S. Environmental Protection Agency's Air Quality System, PlainAirData compiles more than 5,971 county-year air quality records spanning 2020 through 2025, last refreshed in July 2026; see our methodology for the full source list.
National avg good-day share 76.5%
Illustrative reference (not an official EPA target)
Share of monitored days at AQI 0-50 (Good band) averaged across all counties. NAAQS attainment is a pollutant-concentration standard, not a percent-of-days target; 85% is shown here only as an illustrative reference point, not an official EPA benchmark.
Coverage of US counties 31.1%
Target
977 of 3,144 U.S. counties have an active EPA AQS monitor.
Cleanest and most-polluted counties
View all rankings →Cleanest air by typical AQI
Most polluted by typical AQI
How EPA monitoring is distributed
Air-quality data isn't uniform, counties with denser monitoring networks (urban, attainment-classified, or industrial) feed more readings into the AQS database than rural counties. This grid shows where EPA AQS monitors actively report, color-encoded by the share of monitored days that fell in the Good band (AQI 0-50). Sparse coverage is itself a finding: 2,200+ U.S. counties have no active monitor, and what we don't measure, we cannot regulate.
States by Air Quality
View all Scale: 61.2%–67.1% 67.1%–73.0% 73.0%–79.0% 79.0%–84.9% 84.9%–90.8%
Cleanest states right now
Virgin Islands
100.0%1 counties · Avg AQI 18
Hawaii
90.8%3 counties · Avg AQI 28
Montana
90.6%23 counties · Avg AQI 23
Alaska
89.1%8 counties · Avg AQI 20
Puerto Rico
88.4%8 counties · Avg AQI 21
Vermont
88.2%4 counties · Avg AQI 32
Washington
87.9%31 counties · Avg AQI 27
Minnesota
87.8%22 counties · Avg AQI 33
Maine
86.8%11 counties · Avg AQI 36
Virginia
86.1%30 counties · Avg AQI 36
Explore More
Air Quality Guides
Learn how to read and use air quality data from official EPA sources.
Understanding the AQI
What each level means and when to limit outdoor activity.
5 Common Air Pollutants
Ozone, PM2.5, PM10, NO₂, and CO, where they come from and why they matter.
Best & Worst Air Quality
Which US counties have the cleanest and most polluted air.
Best & Worst City Air
Metro rankings and what drives urban air quality.
Air Pollution & Health
Health effects and who is most at risk.
Frequently Asked Questions
What data does PlainAir provide?
PlainAir provides EPA Air Quality System data including annual AQI values for 977 counties, 496 metros, and 50 states + DC + US territories (53 jurisdictions) from 2020-2025.
What is the Air Quality Index?
The AQI is a standardized measure from 0-500 that indicates how clean or polluted the air is. Values below 50 are considered good, while values above 100 may be unhealthy.
Where does PlainAir data come from?
All data comes from the EPA Air Quality System, the official repository of ambient air quality monitoring data from state and local agencies.
Research
Original analysis from our editorial team, every statistic derived from our own database. See all research.
Research
Top 10 US Counties with Most Unhealthy Days in 2024
Explore the 10 counties like San Bernardino, California, with up to 88 unhealthy days in 2024, based on EPA AQS data for 977 counties, revealing key AQI trends and pollutant impacts on public health.
ResearchState Averages of Median AQI Across 2020-2024 in 53 US States
Discover how 50 states + DC + US territories (53 jurisdictions) like Alabama, with an average median AQI of 41.1, trended from 2020 to 2024 using EPA data, including pollutant days for ozone and PM2.5, affecting over 977 counties.
ResearchNational Trends in Good Days Percentage from 2020 to 2024
Analyze nationwide good days trends across 977 counties and 496 metros, with Alabama averaging 77.17% good days and Alaska at 89.09% across 2020-2025, drawn from EPA AQS data on AQI metrics.
About this data
How PlainAir works, and why you can trust these numbers
What this site is
PlainAir turns the U.S. EPA's Air Quality System (AQS) annual county and metro summary files into readable air-quality profiles for 977 counties, 53 states, and every monitored U.S. metro area. Every figure traces back to an EPA-published dataset, never a third-party estimate.
Editorial process
- Source. Download the EPA AQS Annual AQI by County and by CBSA summary files directly from aqs.epa.gov, 2020-2025.
- Verify. Each county and state figure is validated against the source release before publication, and re-checked whenever EPA publishes a new annual file.
- Publish. Compile per-county, per-state, and per-metro profiles with the underlying dataset and vintage documented on the methodology page.
Editorial independence & corrections
The PlainAir editorial team does not accept payment, sponsorship, or promoted placement from government agencies, environmental organizations, or any other covered entity. Found an error? Contact us via the contact page. See our methodology for full source attribution.
Frequently asked
Where does PlainAir's air quality data come from?
Every figure comes from the U.S. EPA's Air Quality System (AQS), the same federal database used for regulatory reporting. We do not run our own monitors or estimate values.
Is this real-time air quality data?
No. PlainAir shows historical annual summaries (2020-2025), not current conditions. For today's AQI, see EPA AirNow.
Is PlainAir affiliated with the EPA?
No. PlainAir is an independent data portal. We present publicly available federal data in a more accessible format but are not affiliated with the U.S. EPA or any government agency.
Every figure on PlainAir is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This homepage summarizes EPA AQS data aggregated across every monitored county, metro, and state. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 2025.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer.