# Share of days with good air quality (US EPA AQI) in Montgomery County

Share of days with good air quality (US EPA AQI) in Montgomery County was 83.1% in 2025. Source: U.S. Environmental Protection Agency.

- Indicator id: `aqi_good_days_share`
- Place id: `us-county-24031`
- Unit: %
- Definition: Days with a daily Air Quality Index of 0 to 50 (good) as a percentage of the days of the year with an AQI in a US county. Calculated by Invokely from the day counts in the EPA AirData annual summaries; both counts are stored with each value.
- Note: United States counties with air quality monitors only, about 1,000 of some 3,100 in recent years; a county without monitors has no value. The number of days with an AQI differs between counties because some monitors run only in the ozone season.
- Source: U.S. Environmental Protection Agency, EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts (https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual)
- Retrieved: 2026-10-12
- License: Public domain (US government work, 17 U.S.C. 105); citation requested
- Citation: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
- Web page: https://invokely.ai/en/good-air-quality-days-share/montgomery-county-maryland
- API: https://invokely.ai/api/v1/series?indicator=aqi_good_days_share&place=us-county-24031

| Period | % |
|---|---:|
| 2025 | 83.1 |
| 2024 | 76.1 |
| 2023 | 81.5 |
| 2022 | 67.9 |
| 2021 | 69.5 |
| 2020 | 87.3 |
| 2019 | 78.7 |
| 2018 | 59.9 |
| 2017 | 74.7 |
| 2016 | 71.9 |
| 2015 | 46.4 |
| 2014 | 55.2 |
| 2013 | 65 |
| 2012 | 45 |
| 2011 | 41.5 |
| 2010 | 41.4 |
| 2009 | 44.1 |
| 2008 | 52.6 |
| 2007 | 49.3 |
| 2006 | 51.6 |
| 2005 | 50.6 |
| 2004 | 55.3 |
| 2003 | 59.4 |
| 2002 | 46.1 |
| 2001 | 48.4 |
| 2000 | 50.4 |
| 1999 | 46.5 |
| 1998 | 45.7 |
| 1997 | 70.2 |
| 1996 | 76.7 |
| 1995 | 77.8 |
| 1994 | 73.4 |
| 1993 | 72.7 |
| 1992 | 85.1 |
| 1991 | 67.7 |
| 1990 | 78.4 |
| 1989 | 75.3 |
| 1988 | 66.9 |
| 1987 | 75.1 |
| 1986 | 61.6 |
| 1985 | 60.3 |
| 1984 | 59.2 |
| 1983 | 63.1 |
| 1982 | 71.9 |
| 1981 | 70.8 |
| 1980 | 75.9 |