EnviroNearby

Fond du Lac County, Wisconsin air quality history

Daily Air Quality Index summaries from EPA monitors in Fond du Lac, Wisconsin, 1984–2025.

91%
Good days in 2025
37
Median daily AQI, 2025
0
Days above 100 in 2025
199
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Fond du Lac, Wisconsin on 199 days. 182 of those days (91%) were in the Good range, and the median daily AQI was 37. That median is about the same as the typical monitored county in Wisconsin (median 38 across 29 counties), and lower than the typical monitored U.S. county (40). The main pollutant was ozone on 199 days. Across the years with fuller monitoring, the share of Good days rose: an average of 73% in 1984–1986 versus 88% in 2023–2025.

EPA did not report an AQI for every day of 2025 here (199 of 365 days). Figures describe monitored days only; seasonal monitoring (for example, ozone measured only in warmer months) can make a county look cleaner or dirtier than a full-year record would.

How the days broke down each year

Each bar is one year. The colored segments show the share of monitored days that fell in each AQI category.

Share of monitored days in each AQI category, by year0%25%50%75%100%1984: Good 135 of 183 days1984: Moderate 36 of 183 days1984: Unhealthy for Sensitive Groups 11 of 183 days1984: Unhealthy 1 of 183 days19841985: Good 115 of 168 days1985: Moderate 36 of 168 days1985: Unhealthy for Sensitive Groups 13 of 168 days1985: Unhealthy 4 of 168 days1986: Good 132 of 173 days1986: Moderate 32 of 173 days1986: Unhealthy for Sensitive Groups 9 of 173 days1987: Good 129 of 179 days1987: Moderate 42 of 179 days1987: Unhealthy for Sensitive Groups 6 of 179 days1987: Unhealthy 2 of 179 days1988: Good 108 of 184 days1988: Moderate 41 of 184 days1988: Unhealthy for Sensitive Groups 25 of 184 days1988: Unhealthy 10 of 184 days1989: Good 125 of 180 days1989: Moderate 40 of 180 days1989: Unhealthy for Sensitive Groups 12 of 180 days1989: Unhealthy 3 of 180 days19891990: Good 151 of 182 days1990: Moderate 28 of 182 days1990: Unhealthy for Sensitive Groups 3 of 182 days1991: Good 146 of 184 days1991: Moderate 32 of 184 days1991: Unhealthy for Sensitive Groups 6 of 184 days1992: Good 137 of 178 days1992: Moderate 28 of 178 days1992: Unhealthy for Sensitive Groups 11 of 178 days1992: Unhealthy 2 of 178 days1993: Good 169 of 184 days1993: Moderate 11 of 184 days1993: Unhealthy for Sensitive Groups 4 of 184 days1994: Good 153 of 176 days1994: Moderate 20 of 176 days1994: Unhealthy for Sensitive Groups 3 of 176 days19941995: Good 146 of 184 days1995: Moderate 25 of 184 days1995: Unhealthy for Sensitive Groups 11 of 184 days1995: Unhealthy 2 of 184 days1996: Good 128 of 179 days1996: Moderate 37 of 179 days1996: Unhealthy for Sensitive Groups 12 of 179 days1996: Unhealthy 2 of 179 days1997: Good 141 of 183 days1997: Moderate 35 of 183 days1997: Unhealthy for Sensitive Groups 6 of 183 days1997: Unhealthy 1 of 183 days1998: Good 115 of 184 days1998: Moderate 61 of 184 days1998: Unhealthy for Sensitive Groups 7 of 184 days1998: Unhealthy 1 of 184 days1999: Good 130 of 184 days1999: Moderate 36 of 184 days1999: Unhealthy for Sensitive Groups 13 of 184 days1999: Unhealthy 5 of 184 days19992000: Good 151 of 180 days2000: Moderate 26 of 180 days2000: Unhealthy for Sensitive Groups 3 of 180 days2001: Good 137 of 184 days2001: Moderate 37 of 184 days2001: Unhealthy for Sensitive Groups 8 of 184 days2001: Unhealthy 2 of 184 days2002: Good 126 of 184 days2002: Moderate 47 of 184 days2002: Unhealthy for Sensitive Groups 9 of 184 days2002: Unhealthy 2 of 184 days2003: Good 133 of 184 days2003: Moderate 38 of 184 days2003: Unhealthy for Sensitive Groups 13 of 184 days2004: Good 167 of 191 days2004: Moderate 22 of 191 days2004: Unhealthy for Sensitive Groups 2 of 191 days20042005: Good 124 of 186 days2005: Moderate 45 of 186 days2005: Unhealthy for Sensitive Groups 16 of 186 days2005: Unhealthy 1 of 186 days2006: Good 146 of 184 days2006: Moderate 37 of 184 days2006: Unhealthy for Sensitive Groups 1 of 184 days2007: Good 152 of 198 days2007: Moderate 39 of 198 days2007: Unhealthy for Sensitive Groups 7 of 198 days2008: Good 180 of 205 days2008: Moderate 25 of 205 days2009: Good 176 of 202 days2009: Moderate 26 of 202 days20092010: Good 190 of 207 days2010: Moderate 16 of 207 days2010: Unhealthy for Sensitive Groups 1 of 207 days2011: Good 176 of 198 days2011: Moderate 15 of 198 days2011: Unhealthy for Sensitive Groups 7 of 198 days2012: Good 151 of 207 days2012: Moderate 41 of 207 days2012: Unhealthy for Sensitive Groups 14 of 207 days2012: Unhealthy 1 of 207 days2013: Good 167 of 189 days2013: Moderate 22 of 189 days2014: Good 165 of 194 days2014: Moderate 27 of 194 days2014: Unhealthy for Sensitive Groups 2 of 194 days20142015: Good 165 of 194 days2015: Moderate 29 of 194 days2016: Good 165 of 189 days2016: Moderate 21 of 189 days2016: Unhealthy for Sensitive Groups 3 of 189 days2017: Good 216 of 236 days2017: Moderate 20 of 236 days2018: Good 213 of 244 days2018: Moderate 30 of 244 days2018: Unhealthy for Sensitive Groups 1 of 244 days2019: Good 195 of 202 days2019: Moderate 7 of 202 days20192020: Good 194 of 205 days2020: Moderate 9 of 205 days2020: Unhealthy for Sensitive Groups 2 of 205 days2021: Good 178 of 208 days2021: Moderate 30 of 208 days2022: Good 193 of 203 days2022: Moderate 9 of 203 days2022: Unhealthy for Sensitive Groups 1 of 203 days2023: Good 162 of 204 days2023: Moderate 38 of 204 days2023: Unhealthy for Sensitive Groups 4 of 204 days2024: Good 190 of 205 days2024: Moderate 15 of 205 days20242025: Good 182 of 199 days2025: Moderate 17 of 199 days2025
  • Good
  • Moderate
  • Unhealthy for Sensitive Groups
  • Unhealthy
  • Very Unhealthy
  • Hazardous

Typical and high-end AQI over time

The median is the middle day of the year. The 90th percentile is the level that only the highest 10% of days exceeded.

Median and 90th-percentile daily AQI, by year0501001501984: 90th percentile AQI 841985: 90th percentile AQI 1011986: 90th percentile AQI 871987: 90th percentile AQI 841988: 90th percentile AQI 1331989: 90th percentile AQI 971990: 90th percentile AQI 641991: 90th percentile AQI 741992: 90th percentile AQI 931993: 90th percentile AQI 501994: 90th percentile AQI 641995: 90th percentile AQI 801996: 90th percentile AQI 871997: 90th percentile AQI 741998: 90th percentile AQI 871999: 90th percentile AQI 1002000: 90th percentile AQI 642001: 90th percentile AQI 842002: 90th percentile AQI 932003: 90th percentile AQI 842004: 90th percentile AQI 582005: 90th percentile AQI 1002006: 90th percentile AQI 642007: 90th percentile AQI 742008: 90th percentile AQI 542009: 90th percentile AQI 582010: 90th percentile AQI 492011: 90th percentile AQI 542012: 90th percentile AQI 902013: 90th percentile AQI 542014: 90th percentile AQI 582015: 90th percentile AQI 582016: 90th percentile AQI 582017: 90th percentile AQI 502018: 90th percentile AQI 542019: 90th percentile AQI 472020: 90th percentile AQI 462021: 90th percentile AQI 542022: 90th percentile AQI 482023: 90th percentile AQI 672024: 90th percentile AQI 492025: 90th percentile AQI 501984: Median AQI 421985: Median AQI 441986: Median AQI 391987: Median AQI 401988: Median AQI 461989: Median AQI 441990: Median AQI 401991: Median AQI 391992: Median AQI 391993: Median AQI 351994: Median AQI 391995: Median AQI 381996: Median AQI 411997: Median AQI 411998: Median AQI 471999: Median AQI 442000: Median AQI 402001: Median AQI 422002: Median AQI 432003: Median AQI 442004: Median AQI 372005: Median AQI 442006: Median AQI 412007: Median AQI 422008: Median AQI 402009: Median AQI 372010: Median AQI 392011: Median AQI 402012: Median AQI 422013: Median AQI 392014: Median AQI 402015: Median AQI 402016: Median AQI 382017: Median AQI 372018: Median AQI 392019: Median AQI 362020: Median AQI 362021: Median AQI 392022: Median AQI 362023: Median AQI 412024: Median AQI 382025: Median AQI 371984198919941999200420092014201920242025
  • Median daily AQI
  • 90th-percentile daily AQI

Main pollutant by day, 2025

On each monitored day, the AQI reflects whichever measured pollutant had the highest index. This counts how many days each pollutant set the AQI. A pollutant that was not measured here cannot appear.

PollutantDays as main pollutantShare of monitored days
Ozone199100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025199182170000375080Ozone
2024205190150000384977Ozone
20232041623840004167122Ozone
2022203193910003648108Ozone
2021208178300000395490Ozone
2020205194920003646115Ozone
2019202195700003647100Ozone
20182442133010003954101Ozone
2017236216200000375093Ozone
20161891652130003858108Ozone
2015194165290000405897Ozone
20141941652720004058105Ozone
2013189167220000395490Ozone
201220715141141004290192Ozone
20111981761570004054140Ozone
20102071901610003949101Ozone
2009202176260000375897Ozone
2008205180250000405497Ozone
20071981523970004274133Ozone
20061841463710004164101Ozone
2005186124451610044100156Ozone
20041911672220003758112Ozone
200318413338130004484136Ozone
20021841264792004393169Ozone
20011841373782004284161Ozone
20001801512630004064150Ozone
1999184130361350044100179Ozone
19981841156171004787164Ozone
19971831413561004174159Ozone
199617912837122004187195Ozone
199518414625112003880169Ozone
19941761532030003964122Ozone
19931841691140003550108Ozone
199217813728112003993159Ozone
19911841463260003974147Ozone
19901821512830004064133Ozone
198918012540123004497185Ozone
19881841084125100046133192Ozone
19871791294262004084166Ozone
19861731323290003987140Ozone
1985168115361340044101164Ozone
198418313536111004284179Ozone

What this data can and can’t tell you

It is a county-level summary. EPA reports one AQI per day for the county, based on the monitors operating there. Air at a particular street, school or home can differ, especially near roads, industry or wildfire smoke.

It is not a health assessment. The AQI is EPA’s scale for communicating daily air quality. A county’s history can’t tell you what the health risk is for any particular person. For daily conditions and health guidance, see AirNow.

Rules change over time. EPA has revised AQI breakpoints, most recently for fine particles in 2024, so some year-to-year change can reflect the scale rather than the air.

Counties in Wisconsin with a similar median AQI in 2025

All monitored counties in Wisconsin

Source: U.S. EPA AirData, “Annual AQI by County” files for 1984–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem