# Share of days with good air quality (US EPA AQI) in Fond du Lac County

Share of days with good air quality (US EPA AQI) in Fond du Lac County was 91.5% in 2025. Source: U.S. Environmental Protection Agency.

- Indicator id: `aqi_good_days_share`
- Place id: `us-county-55039`
- 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/fond-du-lac-county-wisconsin
- API: https://invokely.ai/api/v1/series?indicator=aqi_good_days_share&place=us-county-55039

| Period | % |
|---|---:|
| 2025 | 91.5 |
| 2024 | 92.7 |
| 2023 | 79.4 |
| 2022 | 95.1 |
| 2021 | 85.6 |
| 2020 | 94.6 |
| 2019 | 96.5 |
| 2018 | 87.3 |
| 2017 | 91.5 |
| 2016 | 87.3 |
| 2015 | 85.1 |
| 2014 | 85.1 |
| 2013 | 88.4 |
| 2012 | 72.9 |
| 2011 | 88.9 |
| 2010 | 91.8 |
| 2009 | 87.1 |
| 2008 | 87.8 |
| 2007 | 76.8 |
| 2006 | 79.3 |
| 2005 | 66.7 |
| 2004 | 87.4 |
| 2003 | 72.3 |
| 2002 | 68.5 |
| 2001 | 74.5 |
| 2000 | 83.9 |
| 1999 | 70.7 |
| 1998 | 62.5 |
| 1997 | 77 |
| 1996 | 71.5 |
| 1995 | 79.3 |
| 1994 | 86.9 |
| 1993 | 91.8 |
| 1992 | 77 |
| 1991 | 79.3 |
| 1990 | 83 |
| 1989 | 69.4 |
| 1988 | 58.7 |
| 1987 | 72.1 |
| 1986 | 76.3 |
| 1985 | 68.5 |
| 1984 | 73.8 |