Indicators / United States / Air quality
Days with good air
% of days · U.S. Environmental Protection Agency, AirData annual AQI by county, via airdata.dev · AQI 50 or below, counties with a monitor reading at least 180 days
- Middle county, 2025
- 77.6% of days
- States with a figure
- none county figures only
- Counties with a figure
- 916 2025
Show the numbers (46 rows)
| Year | Middle county |
|---|---|
| 2025 | 77.6 |
| 2024 | 77.7 |
| 2023 | 70.5 |
| 2022 | 76.7 |
| 2021 | 73.3 |
| 2020 | 80.2 |
| 2019 | 77.5 |
| 2018 | 74.4 |
| 2017 | 74.6 |
| 2016 | 77.6 |
| 2015 | 74.7 |
| 2014 | 73.3 |
| 2013 | 72.1 |
| 2012 | 65.1 |
| 2011 | 64.8 |
| 2010 | 65.5 |
| 2009 | 73.2 |
| 2008 | 65.6 |
| 2007 | 59.9 |
| 2006 | 64.7 |
| 2005 | 62.7 |
| 2004 | 70.5 |
| 2003 | 65.7 |
| 2002 | 62.7 |
| 2001 | 62.5 |
| 2000 | 63.1 |
| 1999 | 61.6 |
| 1998 | 69.9 |
| 1997 | 76.2 |
| 1996 | 76.5 |
| 1995 | 74.4 |
| 1994 | 76.0 |
| 1993 | 77.6 |
| 1992 | 80.9 |
| 1991 | 74.5 |
| 1990 | 75.5 |
| 1989 | 74.8 |
| 1988 | 68.2 |
| 1987 | 67.4 |
| 1986 | 72.5 |
| 1985 | 73.0 |
| 1984 | 72.5 |
| 1983 | 71.3 |
| 1982 | 74.3 |
| 1981 | 75.0 |
| 1980 | 71.6 |
Highest and lowest counties, 2025
| Highest | State | Days with good air |
|---|---|---|
| Uinta County | Wyoming | 100.0% of days |
| Carbon County | Wyoming | 100.0% of days |
| Wilson County | Texas | 100.0% of days |
| Karnes County | Texas | 100.0% of days |
| Martin County | North Carolina | 100.0% of days |
| Sonoma County | California | 100.0% of days |
| Pacific County | Washington | 99.7% of days |
| Denali Borough | Alaska | 99.7% of days |
| Navajo County | Arizona | 99.5% of days |
| Lake County | California | 99.2% of days |
| Lowest | State | Days with good air |
|---|---|---|
| Maricopa County | Arizona | 8.8% of days |
| Los Angeles County | California | 10.7% of days |
| Riverside County | California | 10.7% of days |
| Harris County | Texas | 11.0% of days |
| San Bernardino County | California | 12.6% of days |
| Pinal County | Arizona | 17.0% of days |
| Kern County | California | 17.5% of days |
| San Diego County | California | 17.5% of days |
| El Paso County | Texas | 18.1% of days |
| Tulare County | California | 24.1% of days |
Every county's figure is on its own page, in its profile table, with its rank among all counties and within its state.
Get this data
This page's numbers, as JSON:
curl https://visualizedata.org/data/us-indicators/us-good-air-days.jsonEvery place from airdata.dev (live, no key; U.S. Environmental Protection Agency data, this exact version):
curl "https://api.airdata.dev/v1/county-aqi-annual@2026-10-26.271cefd8c0/download/county-aqi-annual.parquet"Source
- U.S. Environmental Protection Agency, AirData annual AQI by county (U.S. public domain): EPA good days / days with an AQI.
- Read through airdata.dev, dataset county-aqi-annual, version 2026-10-26.271cefd8c0; its 47 input files from the U.S. Environmental Protection Agency are named with their sha256 in this page's data, and the site's checks recompute every figure from them.
- A year counts once it is over, for counties whose monitors gave an AQI on at least 180 days; EPA's file for the current year is partial. A county without a monitor has no figure, and one monitor can stand for a large county. Fine-particle (PM2.5) monitors only spread from 1999, and EPA has since tightened the AQI scale for ozone and fine particles, so a long trend mixes changes in the air with changes in what is measured and how.
- EPA refreshes its annual files twice a year; a year is final about May of the next.
- 12 areas in the source are not places in the geo registry and are left out: us-county-02261, us-county-09001, us-county-09003, us-county-09005, us-county-09007, us-county-09009, us-county-09011, us-county-09013, us-county-09015, us-county-78010, us-county-78020, us-county-78030 (Connecticut's former counties, retired Alaska and South Dakota codes, the Virgin Islands).
- Built 2026-10-26.