Data / Rankings / Share of days with good air quality (US EPA AQI) / Counties in Wisconsin

Counties in Wisconsin by share of days with good air quality (US EPA AQI)

Eau Claire County had the highest share of days with good air quality (US EPA AQI) of 35 counties in 2002, at 100%. Waukesha County had the lowest, at 45.5%. The median was 66.5%. Source: EPA.

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Highest100Eau Claire County
Lowest45.5Waukesha County
Median66.535 counties

Map of counties, 2002

Ashland County: 93.1 %Brown County: 64.3 %Columbia County: 68.1 %Dane County: 53.8 %Dodge County: 59.9 %Door County: 69.6 %Douglas County: 74.6 %Eau Claire County: 100 %Florence County: 82.4 %Fond du Lac County: 68.5 %Forest County: 100 %Grant County: 48.3 %Green County: 65.2 %Jefferson County: 54.1 %Kenosha County: 52.2 %Kewaunee County: 69.9 %Manitowoc County: 63.4 %Marathon County: 78.6 %Milwaukee County: 51.5 %Oneida County: 85.2 %Outagamie County: 66.5 %Ozaukee County: 61.5 %Racine County: 86 %Rock County: 55.7 %St. Croix County: 72.2 %Sauk County: 80 %Sheboygan County: 63.6 %Taylor County: 82.6 %Vernon County: 74.3 %Vilas County: 87.3 %Walworth County: 58.8 %Washington County: 64.8 %Waukesha County: 45.5 %Winnebago County: 59.1 %Wood County: 49.2 %
  • Under 54
  • 54 to 62
  • 62 to 67
  • 67 to 74
  • 74 to 83
  • 83 and over
  • No data
%, 2002. Hatched areas have no value for this period. Source: Invokely calculation with data from EPA. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2002

Eau Claire County: 100 %Eau Claire County100Forest County: 100 %Forest County100Ashland County: 93.1 %Ashland County93.1Vilas County: 87.3 %Vilas County87.3Racine County: 86 %Racine County86Oneida County: 85.2 %Oneida County85.2Taylor County: 82.6 %Taylor County82.6Florence County: 82.4 %Florence County82.4Sauk County: 80 %Sauk County80Marathon County: 78.6 %Marathon County78.6Douglas County: 74.6 %Douglas County74.6Vernon County: 74.3 %Vernon County74.3St. Croix County: 72.2 %St. Croix County72.2Kewaunee County: 69.9 %Kewaunee County69.9Door County: 69.6 %Door County69.6Fond du Lac County: 68.5 %Fond du Lac County68.5Columbia County: 68.1 %Columbia County68.1Outagamie County: 66.5 %Outagamie County66.5Green County: 65.2 %Green County65.2Washington County: 64.8 %Washington County64.8Brown County: 64.3 %Brown County64.3Sheboygan County: 63.6 %Sheboygan County63.6Manitowoc County: 63.4 %Manitowoc County63.4Ozaukee County: 61.5 %Ozaukee County61.5Dodge County: 59.9 %Dodge County59.9Winnebago County: 59.1 %Winnebago County59.1Walworth County: 58.8 %Walworth County58.8Rock County: 55.7 %Rock County55.7Jefferson County: 54.1 %Jefferson County54.1Dane County: 53.8 %Dane County53.8Kenosha County: 52.2 %Kenosha County52.2Milwaukee County: 51.5 %Milwaukee County51.5Wood County: 49.2 %Wood County49.2Grant County: 48.3 %Grant County48.3Waukesha County: 45.5 %Waukesha County45.5Eau Claire County: 100 %Eau Claire County100Forest County: 100 %Forest County100Ashland County: 93.1 %Ashland County93.1Vilas County: 87.3 %Vilas County87.3Racine County: 86 %Racine County86Oneida County: 85.2 %Oneida County85.2Taylor County: 82.6 %Taylor County82.6Florence County: 82.4 %Florence County82.4Sauk County: 80 %Sauk County80Marathon County: 78.6 %Marathon County78.6Douglas County: 74.6 %Douglas County74.6Vernon County: 74.3 %Vernon County74.3St. Croix County: 72.2 %St. Croix County72.2Kewaunee County: 69.9 %Kewaunee County69.9Door County: 69.6 %Door County69.6Fond du Lac County: 68.5 %Fond du Lac County68.5Columbia County: 68.1 %Columbia County68.1Outagamie County: 66.5 %Outagamie County66.5Green County: 65.2 %Green County65.2Washington County: 64.8 %Washington County64.8Brown County: 64.3 %Brown County64.3Sheboygan County: 63.6 %Sheboygan County63.6Manitowoc County: 63.4 %Manitowoc County63.4Ozaukee County: 61.5 %Ozaukee County61.5Dodge County: 59.9 %Dodge County59.9Winnebago County: 59.1 %Winnebago County59.1Walworth County: 58.8 %Walworth County58.8Rock County: 55.7 %Rock County55.7Jefferson County: 54.1 %Jefferson County54.1Dane County: 53.8 %Dane County53.8Kenosha County: 52.2 %Kenosha County52.2Milwaukee County: 51.5 %Milwaukee County51.5Wood County: 49.2 %Wood County49.2Grant County: 48.3 %Grant County48.3Waukesha County: 45.5 %Waukesha County45.5
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2002 (%)Change on 2001
1Eau Claire County100n/a
1Forest County100n/a
3Ashland County93.1-6.9 pts
4Vilas County87.3+4.1 pts
5Racine County86-1.4 pts
6Oneida County85.2+6.3 pts
7Taylor County82.6-2.9 pts
8Florence County82.4-0.8 pts
9Sauk County80+5.1 pts
10Marathon County78.6-1.5 pts
11Douglas County74.6+5.7 pts
12Vernon County74.3-5 pts
13St. Croix County72.2-6.7 pts
14Kewaunee County69.9-9.4 pts
15Door County69.6-0.2 pts
16Fond du Lac County68.5-6 pts
17Columbia County68.1-7.3 pts
18Outagamie County66.5+0.1 pts
19Green County65.2-3.7 pts
20Washington County64.8-11.1 pts
21Brown County64.3+0.1 pts
22Sheboygan County63.6-0.5 pts
23Manitowoc County63.40 pts
24Ozaukee County61.5+4.7 pts
25Dodge County59.9-11.3 pts
26Winnebago County59.1-7 pts
27Walworth County58.8-4.2 pts
28Rock County55.7+4.7 pts
29Jefferson County54.1-3.1 pts
30Dane County53.8-10.1 pts
31Kenosha County52.2+4 pts
32Milwaukee County51.5+21.9 pts
33Wood County49.2-8.7 pts
34Grant County48.3+4.4 pts
35Waukesha County45.5+9.3 pts

Other periods

About this ranking

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.

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.

Every value in the ranking comes from the same publisher and the same period, so the counties are compared on one definition. 13 counties with data in other periods have no value for 2002 and are left out rather than filled from another source. Equal values share a rank.

How to cite

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.

Citation styles

The publisher is the author. Invokely is named only as the place the figures were read, where a style asks for it.

APA 7

U.S. Environmental Protection Agency. (2026). EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts (Counties in Wisconsin by share of days with good air quality (US EPA AQI), 2002) [Data set]. Retrieved October 12, 2026, from https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual

MLA 9

EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts, Counties in Wisconsin by share of days with good air quality (US EPA AQI), 2002. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/good-air-quality-days-share/wisconsin-counties?period=2002. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. Counties in Wisconsin by share of days with good air quality (US EPA AQI), 2002. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/good-air-quality-days-share/wisconsin-counties?period=2002.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts, Counties in Wisconsin by share of days with good air quality (US EPA AQI), 2002 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/good-air-quality-days-share/wisconsin-counties?period=2002 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_wisconsin_by_2002,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts: Counties in Wisconsin by share of days with good air quality (US EPA AQI), 2002}},
  year = {2026},
  howpublished = {Data set},
  url = {https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual},
  urldate = {2026-10-12},
  note = {Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/wisconsin-counties?period=2002. Publisher attribution: 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.},
}
RIS
TY  - DATA
AU  - U.S. Environmental Protection Agency
TI  - EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts: Counties in Wisconsin by share of days with good air quality (US EPA AQI), 2002
PY  - 2026
DA  - 2026/07/13
PB  - U.S. Environmental Protection Agency
DB  - Invokely
UR  - https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual
L2  - https://invokely.ai/rankings/good-air-quality-days-share/wisconsin-counties?period=2002
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/wisconsin-counties?period=2002.
N1  - Publisher attribution: 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.
ER  -
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Questions

Which county has the highest share of days with good air quality (US EPA AQI)?

Eau Claire County, with 100% in 2002, according to EPA.

Which county has the lowest share of days with good air quality (US EPA AQI)?

Waukesha County, with 45.5% in 2002.

Where does this ranking come from?

Every value comes from one source and one period, so the places are comparable: 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. Retrieved 2026-10-12. 13 counties have no value for 2002 and are not ranked.

Share of days with good air quality (US EPA AQI): other rankings

Counties in Wisconsin: more rankings