EnviroNearby

Dane County, Wisconsin air quality history

Daily Air Quality Index summaries from EPA monitors in Dane, Wisconsin, 1980–2025.

67%
Good days in 2025
41
Median daily AQI, 2025
6
Days above 100 in 2025
365
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Dane, Wisconsin on 365 days. 246 of those days (67%) were in the Good range, and the median daily AQI was 41. That median is higher than the typical monitored county in Wisconsin (median 38 across 29 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 256 days. Across the years with fuller monitoring, the share of Good days fell: an average of 82% in 1980–1982 versus 63% in 2023–2025.

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%1980: Good 196 of 265 days1980: Moderate 52 of 265 days1980: Unhealthy for Sensitive Groups 16 of 265 days1980: Unhealthy 1 of 265 days19801981: Good 280 of 319 days1981: Moderate 31 of 319 days1981: Unhealthy for Sensitive Groups 8 of 319 days1982: Good 289 of 344 days1982: Moderate 48 of 344 days1982: Unhealthy for Sensitive Groups 5 of 344 days1982: Unhealthy 2 of 344 days1983: Good 303 of 360 days1983: Moderate 35 of 360 days1983: Unhealthy for Sensitive Groups 18 of 360 days1983: Unhealthy 4 of 360 days1984: Good 318 of 365 days1984: Moderate 35 of 365 days1984: Unhealthy for Sensitive Groups 11 of 365 days1984: Unhealthy 1 of 365 days1985: Good 311 of 365 days1985: Moderate 43 of 365 days1985: Unhealthy for Sensitive Groups 10 of 365 days1985: Unhealthy 1 of 365 days19851986: Good 319 of 365 days1986: Moderate 36 of 365 days1986: Unhealthy for Sensitive Groups 10 of 365 days1987: Good 306 of 365 days1987: Moderate 47 of 365 days1987: Unhealthy for Sensitive Groups 10 of 365 days1987: Unhealthy 2 of 365 days1988: Good 278 of 366 days1988: Moderate 52 of 366 days1988: Unhealthy for Sensitive Groups 26 of 366 days1988: Unhealthy 10 of 366 days1989: Good 298 of 365 days1989: Moderate 51 of 365 days1989: Unhealthy for Sensitive Groups 15 of 365 days1989: Unhealthy 1 of 365 days1990: Good 331 of 365 days1990: Moderate 32 of 365 days1990: Unhealthy for Sensitive Groups 2 of 365 days19901991: Good 308 of 365 days1991: Moderate 43 of 365 days1991: Unhealthy for Sensitive Groups 11 of 365 days1991: Unhealthy 3 of 365 days1992: Good 326 of 364 days1992: Moderate 23 of 364 days1992: Unhealthy for Sensitive Groups 13 of 364 days1992: Unhealthy 2 of 364 days1993: Good 350 of 365 days1993: Moderate 12 of 365 days1993: Unhealthy for Sensitive Groups 3 of 365 days1994: Good 340 of 365 days1994: Moderate 21 of 365 days1994: Unhealthy for Sensitive Groups 4 of 365 days1995: Good 317 of 360 days1995: Moderate 34 of 360 days1995: Unhealthy for Sensitive Groups 6 of 360 days1995: Unhealthy 3 of 360 days19951996: Good 336 of 366 days1996: Moderate 24 of 366 days1996: Unhealthy for Sensitive Groups 5 of 366 days1996: Unhealthy 1 of 366 days1997: Good 318 of 365 days1997: Moderate 40 of 365 days1997: Unhealthy for Sensitive Groups 7 of 365 days1998: Good 232 of 301 days1998: Moderate 58 of 301 days1998: Unhealthy for Sensitive Groups 10 of 301 days1998: Unhealthy 1 of 301 days1999: Good 181 of 297 days1999: Moderate 102 of 297 days1999: Unhealthy for Sensitive Groups 11 of 297 days1999: Unhealthy 3 of 297 days2000: Good 273 of 366 days2000: Moderate 88 of 366 days2000: Unhealthy for Sensitive Groups 5 of 366 days20002001: Good 200 of 313 days2001: Moderate 101 of 313 days2001: Unhealthy for Sensitive Groups 11 of 313 days2001: Unhealthy 1 of 313 days2002: Good 135 of 251 days2002: Moderate 101 of 251 days2002: Unhealthy for Sensitive Groups 15 of 251 days2003: Good 134 of 245 days2003: Moderate 99 of 245 days2003: Unhealthy for Sensitive Groups 11 of 245 days2003: Unhealthy 1 of 245 days2004: Good 163 of 241 days2004: Moderate 74 of 241 days2004: Unhealthy for Sensitive Groups 4 of 241 days2005: Good 133 of 257 days2005: Moderate 112 of 257 days2005: Unhealthy for Sensitive Groups 12 of 257 days20052006: Good 200 of 305 days2006: Moderate 104 of 305 days2006: Unhealthy for Sensitive Groups 1 of 305 days2007: Good 138 of 364 days2007: Moderate 209 of 364 days2007: Unhealthy for Sensitive Groups 16 of 364 days2007: Unhealthy 1 of 364 days2008: Good 146 of 358 days2008: Moderate 209 of 358 days2008: Unhealthy for Sensitive Groups 3 of 358 days2009: Good 186 of 365 days2009: Moderate 174 of 365 days2009: Unhealthy for Sensitive Groups 5 of 365 days2010: Good 117 of 354 days2010: Moderate 233 of 354 days2010: Unhealthy for Sensitive Groups 4 of 354 days20102011: Good 182 of 359 days2011: Moderate 176 of 359 days2011: Unhealthy for Sensitive Groups 1 of 359 days2012: Good 158 of 355 days2012: Moderate 187 of 355 days2012: Unhealthy for Sensitive Groups 8 of 355 days2012: Unhealthy 2 of 355 days2013: Good 182 of 365 days2013: Moderate 183 of 365 days2014: Good 199 of 365 days2014: Moderate 164 of 365 days2014: Unhealthy for Sensitive Groups 2 of 365 days2015: Good 224 of 347 days2015: Moderate 122 of 347 days2015: Unhealthy for Sensitive Groups 1 of 347 days20152016: Good 246 of 361 days2016: Moderate 115 of 361 days2017: Good 241 of 358 days2017: Moderate 117 of 358 days2018: Good 215 of 365 days2018: Moderate 148 of 365 days2018: Unhealthy for Sensitive Groups 2 of 365 days2019: Good 239 of 365 days2019: Moderate 126 of 365 days2020: Good 222 of 366 days2020: Moderate 142 of 366 days2020: Unhealthy for Sensitive Groups 2 of 366 days20202021: Good 199 of 365 days2021: Moderate 165 of 365 days2021: Unhealthy for Sensitive Groups 1 of 365 days2022: Good 236 of 365 days2022: Moderate 129 of 365 days2023: Good 184 of 365 days2023: Moderate 157 of 365 days2023: Unhealthy for Sensitive Groups 20 of 365 days2023: Unhealthy 1 of 365 days2023: Very Unhealthy 3 of 365 days2024: Good 264 of 366 days2024: Moderate 102 of 366 days2025: Good 246 of 365 days2025: Moderate 113 of 365 days2025: Unhealthy for Sensitive Groups 5 of 365 days2025: Unhealthy 1 of 365 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 year0501001980: 90th percentile AQI 901981: 90th percentile AQI 581982: 90th percentile AQI 611983: 90th percentile AQI 771984: 90th percentile AQI 611985: 90th percentile AQI 611986: 90th percentile AQI 581987: 90th percentile AQI 741988: 90th percentile AQI 1001989: 90th percentile AQI 641990: 90th percentile AQI 501991: 90th percentile AQI 581992: 90th percentile AQI 511993: 90th percentile AQI 441994: 90th percentile AQI 481995: 90th percentile AQI 571996: 90th percentile AQI 491997: 90th percentile AQI 581998: 90th percentile AQI 801999: 90th percentile AQI 812000: 90th percentile AQI 712001: 90th percentile AQI 802002: 90th percentile AQI 872003: 90th percentile AQI 872004: 90th percentile AQI 682005: 90th percentile AQI 902006: 90th percentile AQI 702007: 90th percentile AQI 842008: 90th percentile AQI 752009: 90th percentile AQI 752010: 90th percentile AQI 752011: 90th percentile AQI 732012: 90th percentile AQI 802013: 90th percentile AQI 682014: 90th percentile AQI 662015: 90th percentile AQI 642016: 90th percentile AQI 642017: 90th percentile AQI 612018: 90th percentile AQI 672019: 90th percentile AQI 642020: 90th percentile AQI 632021: 90th percentile AQI 682022: 90th percentile AQI 622023: 90th percentile AQI 802024: 90th percentile AQI 582025: 90th percentile AQI 641980: Median AQI 371981: Median AQI 301982: Median AQI 341983: Median AQI 311984: Median AQI 341985: Median AQI 351986: Median AQI 311987: Median AQI 291988: Median AQI 321989: Median AQI 311990: Median AQI 281991: Median AQI 271992: Median AQI 271993: Median AQI 301994: Median AQI 321995: Median AQI 311996: Median AQI 281997: Median AQI 291998: Median AQI 371999: Median AQI 442000: Median AQI 352001: Median AQI 432002: Median AQI 482003: Median AQI 492004: Median AQI 422005: Median AQI 492006: Median AQI 432007: Median AQI 542008: Median AQI 542009: Median AQI 492010: Median AQI 552011: Median AQI 502012: Median AQI 522013: Median AQI 512014: Median AQI 472015: Median AQI 442016: Median AQI 412017: Median AQI 422018: Median AQI 462019: Median AQI 432020: Median AQI 442021: Median AQI 482022: Median AQI 452023: Median AQI 502024: Median AQI 422025: Median AQI 411980198519901995200020052010201520202025
  • 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
Fine particles (PM2.5)25670%
Ozone10930%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
202536524611351004164170PM2.5
20243662641020000425893PM2.5
2023365184157201305080268PM2.5
20223652361290000456291PM2.5
202136519916510004868101PM2.5
202036622214220004463112PM2.5
20193652391260000436493PM2.5
201836521514820004667112PM2.5
20173582411170000426186PM2.5
201636124611500004164100PM2.5
201534722412210004464106PM2.5
201436519916420004766112PM2.5
20133651821830000516893PM2.5
201235515818782005280154PM2.5
201135918217610005073106PM2.5
201035411723340005575125PM2.5
200936518617450004975111PM2.5
200835814620930005475127PM2.5
2007364138209161005484155PM2.5
200630520010410004370146Ozone
2005257133112120004990143Ozone
20042411637440004268124Ozone
200324513499111004987154Ozone
2002251135101150004887147Ozone
2001313200101111004380164Ozone
20003662738850003571122Ozone
1999297181102113004481174Ozone
199830123258101003780154Ozone
19973653184070002958150CO
19963663362451002849159CO
19953603173463003157174CO
19943653402140003248119CO
19933653501230003044136CO
199236432623132002751154Ozone
199136530843113002758166Ozone
19903653313220002850140Ozone
198936529851151003164190Ozone
19883662785226100032100187Ozone
198736530647102002974169Ozone
198636531936100003158136Ozone
198536531143101003561156Ozone
198436531835111003461151Ozone
198336030335184003177182Ozone
19823442894852003461187Ozone
19813192803180003058140Ozone
198026519652161003790156Ozone

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 1980–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem