EnviroNearby

Waukesha County, Wisconsin air quality history

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

66%
Good days in 2025
41
Median daily AQI, 2025
10
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 Waukesha, Wisconsin on 365 days. 242 of those days (66%) 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 248 days. Across the years with fuller monitoring, the share of Good days fell: an average of 87% in 1980–1982 versus 62% 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 342 of 362 days1980: Moderate 16 of 362 days1980: Unhealthy for Sensitive Groups 3 of 362 days1980: Unhealthy 1 of 362 days19801981: Good 297 of 357 days1981: Moderate 35 of 357 days1981: Unhealthy for Sensitive Groups 16 of 357 days1981: Unhealthy 7 of 357 days1981: Very Unhealthy 2 of 357 days1982: Good 305 of 363 days1982: Moderate 41 of 363 days1982: Unhealthy for Sensitive Groups 12 of 363 days1982: Unhealthy 5 of 363 days1983: Good 279 of 358 days1983: Moderate 47 of 358 days1983: Unhealthy for Sensitive Groups 22 of 358 days1983: Unhealthy 9 of 358 days1983: Very Unhealthy 1 of 358 days1984: Good 300 of 365 days1984: Moderate 54 of 365 days1984: Unhealthy for Sensitive Groups 10 of 365 days1984: Unhealthy 1 of 365 days1985: Good 312 of 364 days1985: Moderate 39 of 364 days1985: Unhealthy for Sensitive Groups 11 of 364 days1985: Unhealthy 2 of 364 days19851986: Good 285 of 365 days1986: Moderate 68 of 365 days1986: Unhealthy for Sensitive Groups 9 of 365 days1986: Unhealthy 3 of 365 days1987: Good 281 of 363 days1987: Moderate 63 of 363 days1987: Unhealthy for Sensitive Groups 11 of 363 days1987: Unhealthy 5 of 363 days1987: Very Unhealthy 3 of 363 days1988: Good 280 of 366 days1988: Moderate 47 of 366 days1988: Unhealthy for Sensitive Groups 30 of 366 days1988: Unhealthy 9 of 366 days1989: Good 250 of 365 days1989: Moderate 93 of 365 days1989: Unhealthy for Sensitive Groups 16 of 365 days1989: Unhealthy 4 of 365 days1989: Very Unhealthy 2 of 365 days1990: Good 282 of 365 days1990: Moderate 73 of 365 days1990: Unhealthy for Sensitive Groups 9 of 365 days1990: Unhealthy 1 of 365 days19901991: Good 300 of 365 days1991: Moderate 42 of 365 days1991: Unhealthy for Sensitive Groups 18 of 365 days1991: Unhealthy 5 of 365 days1992: Good 334 of 366 days1992: Moderate 22 of 366 days1992: Unhealthy for Sensitive Groups 9 of 366 days1992: Unhealthy 1 of 366 days1993: Good 331 of 365 days1993: Moderate 26 of 365 days1993: Unhealthy for Sensitive Groups 8 of 365 days1994: Good 330 of 364 days1994: Moderate 29 of 364 days1994: Unhealthy for Sensitive Groups 4 of 364 days1994: Unhealthy 1 of 364 days1995: Good 318 of 365 days1995: Moderate 35 of 365 days1995: Unhealthy for Sensitive Groups 8 of 365 days1995: Unhealthy 4 of 365 days19951996: Good 341 of 366 days1996: Moderate 19 of 366 days1996: Unhealthy for Sensitive Groups 4 of 366 days1996: Unhealthy 2 of 366 days1997: Good 306 of 364 days1997: Moderate 53 of 364 days1997: Unhealthy for Sensitive Groups 2 of 364 days1997: Unhealthy 3 of 364 days1998: Good 284 of 363 days1998: Moderate 70 of 363 days1998: Unhealthy for Sensitive Groups 9 of 363 days1999: Good 241 of 365 days1999: Moderate 98 of 365 days1999: Unhealthy for Sensitive Groups 19 of 365 days1999: Unhealthy 7 of 365 days2000: Good 129 of 366 days2000: Moderate 228 of 366 days2000: Unhealthy for Sensitive Groups 8 of 366 days2000: Unhealthy 1 of 366 days20002001: Good 132 of 365 days2001: Moderate 207 of 365 days2001: Unhealthy for Sensitive Groups 23 of 365 days2001: Unhealthy 3 of 365 days2002: Good 166 of 365 days2002: Moderate 184 of 365 days2002: Unhealthy for Sensitive Groups 13 of 365 days2002: Unhealthy 2 of 365 days2003: Good 175 of 348 days2003: Moderate 164 of 348 days2003: Unhealthy for Sensitive Groups 8 of 348 days2003: Unhealthy 1 of 348 days2004: Good 235 of 347 days2004: Moderate 105 of 347 days2004: Unhealthy for Sensitive Groups 7 of 347 days2005: Good 202 of 336 days2005: Moderate 108 of 336 days2005: Unhealthy for Sensitive Groups 25 of 336 days2005: Unhealthy 1 of 336 days20052006: Good 255 of 365 days2006: Moderate 107 of 365 days2006: Unhealthy for Sensitive Groups 3 of 365 days2007: Good 242 of 364 days2007: Moderate 116 of 364 days2007: Unhealthy for Sensitive Groups 6 of 364 days2008: Good 264 of 366 days2008: Moderate 100 of 366 days2008: Unhealthy for Sensitive Groups 2 of 366 days2009: Good 230 of 317 days2009: Moderate 85 of 317 days2009: Unhealthy for Sensitive Groups 2 of 317 days2010: Good 173 of 252 days2010: Moderate 76 of 252 days2010: Unhealthy for Sensitive Groups 3 of 252 days20102011: Good 168 of 283 days2011: Moderate 111 of 283 days2011: Unhealthy for Sensitive Groups 4 of 283 days2012: Good 120 of 353 days2012: Moderate 222 of 353 days2012: Unhealthy for Sensitive Groups 10 of 353 days2012: Unhealthy 1 of 353 days2013: Good 193 of 362 days2013: Moderate 169 of 362 days2014: Good 188 of 356 days2014: Moderate 165 of 356 days2014: Unhealthy for Sensitive Groups 3 of 356 days2015: Good 219 of 357 days2015: Moderate 137 of 357 days2015: Unhealthy for Sensitive Groups 1 of 357 days20152016: Good 219 of 360 days2016: Moderate 141 of 360 days2017: Good 232 of 359 days2017: Moderate 127 of 359 days2018: Good 213 of 365 days2018: Moderate 149 of 365 days2018: Unhealthy for Sensitive Groups 3 of 365 days2019: Good 211 of 365 days2019: Moderate 153 of 365 days2019: Unhealthy for Sensitive Groups 1 of 365 days2020: Good 214 of 359 days2020: Moderate 143 of 359 days2020: Unhealthy for Sensitive Groups 2 of 359 days20202021: Good 177 of 365 days2021: Moderate 184 of 365 days2021: Unhealthy for Sensitive Groups 4 of 365 days2022: Good 215 of 363 days2022: Moderate 144 of 363 days2022: Unhealthy for Sensitive Groups 4 of 363 days2023: Good 171 of 360 days2023: Moderate 167 of 360 days2023: Unhealthy for Sensitive Groups 19 of 360 days2023: Unhealthy 1 of 360 days2023: Very Unhealthy 2 of 360 days2024: Good 260 of 366 days2024: Moderate 105 of 366 days2024: Unhealthy for Sensitive Groups 1 of 366 days2025: Good 242 of 365 days2025: Moderate 113 of 365 days2025: Unhealthy for Sensitive Groups 7 of 365 days2025: Unhealthy 3 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 year0501001501980: 90th percentile AQI 431981: 90th percentile AQI 761982: 90th percentile AQI 691983: 90th percentile AQI 971984: 90th percentile AQI 641985: 90th percentile AQI 641986: 90th percentile AQI 661987: 90th percentile AQI 701988: 90th percentile AQI 1051989: 90th percentile AQI 801990: 90th percentile AQI 641991: 90th percentile AQI 801992: 90th percentile AQI 491993: 90th percentile AQI 501994: 90th percentile AQI 501995: 90th percentile AQI 581996: 90th percentile AQI 461997: 90th percentile AQI 641998: 90th percentile AQI 731999: 90th percentile AQI 872000: 90th percentile AQI 812001: 90th percentile AQI 912002: 90th percentile AQI 832003: 90th percentile AQI 802004: 90th percentile AQI 672005: 90th percentile AQI 902006: 90th percentile AQI 702007: 90th percentile AQI 722008: 90th percentile AQI 672009: 90th percentile AQI 672010: 90th percentile AQI 652011: 90th percentile AQI 702012: 90th percentile AQI 752013: 90th percentile AQI 662014: 90th percentile AQI 692015: 90th percentile AQI 652016: 90th percentile AQI 632017: 90th percentile AQI 632018: 90th percentile AQI 672019: 90th percentile AQI 642020: 90th percentile AQI 642021: 90th percentile AQI 712022: 90th percentile AQI 632023: 90th percentile AQI 802024: 90th percentile AQI 612025: 90th percentile AQI 691980: Median AQI 211981: Median AQI 281982: Median AQI 321983: Median AQI 311984: Median AQI 311985: Median AQI 281986: Median AQI 311987: Median AQI 341988: Median AQI 311989: Median AQI 391990: Median AQI 341991: Median AQI 281992: Median AQI 261993: Median AQI 281994: Median AQI 271995: Median AQI 261996: Median AQI 241997: Median AQI 241998: Median AQI 311999: Median AQI 372000: Median AQI 572001: Median AQI 562002: Median AQI 532003: Median AQI 502004: Median AQI 392005: Median AQI 432006: Median AQI 362007: Median AQI 362008: Median AQI 362009: Median AQI 342010: Median AQI 412011: Median AQI 442012: Median AQI 562013: Median AQI 472014: Median AQI 492015: Median AQI 442016: Median AQI 442017: Median AQI 432018: Median AQI 462019: Median AQI 452020: Median AQI 442021: Median AQI 512022: Median AQI 472023: Median AQI 522024: Median AQI 432025: 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)24868%
Ozone11632%
Coarse particles (PM10)1<1%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
202536524211373004169172PM2.5
202436626010510004361101PM2.5
2023360171167191205280270PM2.5
202236321514440004763126PM2.5
202136517718440005171108PM2.5
202035921414320004464129PM2.5
201936521115310004564115PM2.5
201836521314930004667122PM2.5
20173592321270000436391PM2.5
201636021914100004463100PM2.5
201535721913710004465105PM2.5
201435618816530004969112PM2.5
20133621931690000476684PM2.5
2012353120222101005675159PM2.5
201128316811140004470115Ozone
20102521737630004165119Ozone
20093172308520003467123Ozone
200836626410020003667132Ozone
200736424211660003672134Ozone
200636525510730003670129Ozone
2005336202108251004390159Ozone
200434723510570003967139PM2.5
200334817516481005080154PM2.5
2002365166184132005383172PM2.5
2001365132207233005691161PM2.5
200036612922881005781151PM2.5
199936524198197003787192Ozone
19983632847090003173150Ozone
19973643065323002464177Ozone
19963663411942002446161Ozone
19953653183584002658192Ozone
19943643302941002750164Ozone
19933653312680002850136Ozone
19923663342291002649164Ozone
199136530042185002880182Ozone
19903652827391003464169PM10
198936525093164203980209PM10
1988366280473090031105200Ozone
198736328163115303470208Ozone
19863652856893003166159Ozone
198536431239112002864164CO
198436530054101003164174CO
198335827947229103197209Ozone
198236330541125003269190Ozone
198135729735167202876204Ozone
19803623421631002143154CO

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