National ranking · cleanest air

Best Air Quality in the US (2025)

Ranked by the highest share of Good air days among counties with at least 100 monitored days in 2025, the counties where residents breathe the cleanest air most often, from EPA Air Quality System monitoring.

99.7%
#1 Pacific, Washington
30
Counties ranked

Pacific County, Washington leads the 2025 cleanest-air list among 30 ranked U.S. counties (99.7% Good)

According to the U.S. EPA Air Quality System, this ranking orders 30 counties with at least 100 monitored days in 2025 by the highest share of days in the Good AQI band, using median AQI to separate near-ties. It describes a historical reporting year, not today's air quality. For current conditions and alerts, use AirNow.

Data source EPA Air Quality System (AQS)

#1 Good-day share
Pacific County, Washington ranks #1 of 30 for Good-day share at 99.7%.
#1 median AQI
#1 median AQI: 16
Counties ranked
Counties ranked: 30
Tied at 100% Good
Tied at 100% Good: 0

from the compiled EPA AQS release in this database.

Counties below the 100-day monitoring floor are excluded: with only a handful of readings, a single clean stretch can push a county to a 100% Good-day rate that a normal year's weather would not hold up. 0 counties tie at 100.0% with this floor applied, all with a genuinely large sample of monitored days. For comparison, the cohort median across all 951 floor-qualifying counties is 77.5%, meaning the difference between a top-ranked county and a typical monitored county is real, not sampling noise.

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Filters keep the Good-day-share ranking contract. A state filter ranks that state's qualifying counties; pollutant filters keep rows whose annual day-type count is led by ozone, PM2.5, or PM10. Raising the monitored-days floor tightens the sample beyond the default 100-day Module-34 guard.

Compare up to three counties

Showing 30 matching Washington counties . Back to the national top 50.

Where the national cleanest cohort concentrates

Among the unfiltered national top 50 (highest Good-day share, ≥100 monitored days), Virginia contributes 6 counties , followed by Wyoming (4). State filters rank every qualifying county inside one jurisdiction.

Compare any two counties

For a side-by-side annual change view, open the county compare tool.

Cleanest of the clean: lowest median AQI

Cleanest of the clean: lowest median AQI

Among the top counties (all near a 100% Good-day record), the lowest typical AQI. Shorter is cleaner.

  1. 1 Pacific, Washington 16
  2. 2 Garfield, Washington 19
  3. 3 Jefferson, Washington 20
  4. 4 Lewis, Washington 20
  5. 5 Adams, Washington 21
  6. 6 Grays Harbor, Washington 22
  7. 7 Kitsap, Washington 22
  8. 8 Cowlitz, Washington 22
  9. 9 Mason, Washington 23
  10. 10 Whitman, Washington 23
  11. 11 Franklin, Washington 23
  12. 12 Skagit, Washington 25

Median AQI · EPA Air Quality System

Ranked counties

# County State Good Days % Median AQI
1 Pacific Washington 99.7% 16 Good
2 Skagit Washington 97.5% 25 Good
3 Jefferson Washington 97.3% 20 Good
4 Grays Harbor Washington 97.3% 22 Good
5 Kitsap Washington 95.5% 22 Good
6 Whatcom Washington 94.0% 31 Good
7 Thurston Washington 93.5% 27 Good
8 Garfield Washington 92.5% 19 Good
9 Lewis Washington 91.3% 20 Good
10 Adams Washington 90.5% 21 Good
11 Mason Washington 90.4% 23 Good
12 Columbia Washington 90.4% 36 Good
13 Cowlitz Washington 90.4% 22 Good
14 Whitman Washington 86.8% 23 Good
15 Franklin Washington 86.7% 23 Good
16 Clallam Washington 85.5% 29 Good
17 Clark Washington 82.7% 33 Good
18 Walla Walla Washington 80.8% 28 Good
19 Benton Washington 80.3% 36 Good
20 Kittitas Washington 80.0% 25 Good
21 Grant Washington 79.7% 28 Good
22 Pierce Washington 73.2% 44 Good
23 Chelan Washington 69.6% 35 Good
24 Stevens Washington 69.0% 35 Good
25 Snohomish Washington 68.0% 41 Good
26 King Washington 67.1% 43 Good
27 Spokane Washington 64.7% 43 Good
28 Yakima Washington 61.9% 41 Good
29 Asotin Washington 61.9% 42 Good
30 Okanogan Washington 56.5% 41 Good

Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS). Good Days % is the share of monitored days with AQI at or below 50. Counties ranked by good_pct descending

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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.