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)

Chippewa County had the highest share of days with good air quality (US EPA AQI) of 33 counties in 2010, at 100%. Dane County had the lowest, at 33.1%. The median was 84.2%. Source: EPA.

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Highest100Chippewa County
Lowest33.1Dane County
Median84.233 counties

Map of counties, 2010

Ashland County: 92.8 %Brown County: 56.7 %Chippewa County: 100 %Columbia County: 88.8 %Dane County: 33.1 %Dodge County: 59 %Door County: 85.2 %Eau Claire County: 61.9 %Florence County: 92.1 %Fond du Lac County: 91.8 %Forest County: 90.6 %Grant County: 55.8 %Jefferson County: 86.6 %Kenosha County: 58.6 %Kewaunee County: 84.5 %La Crosse County: 69.7 %Manitowoc County: 78.4 %Marathon County: 93.8 %Milwaukee County: 61.6 %Oneida County: 90.5 %Outagamie County: 79.7 %Ozaukee County: 72.3 %Racine County: 75 %Rock County: 85.5 %St. Croix County: 76.5 %Sauk County: 78.9 %Sheboygan County: 77.2 %Taylor County: 88.7 %Vernon County: 89.8 %Vilas County: 89.1 %Walworth County: 84.2 %Washington County: 90.7 %Waukesha County: 68.7 %
  • Under 62
  • 62 to 76
  • 76 to 84
  • 84 to 89
  • 89 to 91
  • 91 and over
  • No data
%, 2010. 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, 2010

Chippewa County: 100 %Chippewa County100Marathon County: 93.8 %Marathon County93.8Ashland County: 92.8 %Ashland County92.8Florence County: 92.1 %Florence County92.1Fond du Lac County: 91.8 %Fond du Lac County91.8Washington County: 90.7 %Washington County90.7Forest County: 90.6 %Forest County90.6Oneida County: 90.5 %Oneida County90.5Vernon County: 89.8 %Vernon County89.8Vilas County: 89.1 %Vilas County89.1Columbia County: 88.8 %Columbia County88.8Taylor County: 88.7 %Taylor County88.7Jefferson County: 86.6 %Jefferson County86.6Rock County: 85.5 %Rock County85.5Door County: 85.2 %Door County85.2Kewaunee County: 84.5 %Kewaunee County84.5Walworth County: 84.2 %Walworth County84.2Outagamie County: 79.7 %Outagamie County79.7Sauk County: 78.9 %Sauk County78.9Manitowoc County: 78.4 %Manitowoc County78.4Sheboygan County: 77.2 %Sheboygan County77.2St. Croix County: 76.5 %St. Croix County76.5Racine County: 75 %Racine County75Ozaukee County: 72.3 %Ozaukee County72.3La Crosse County: 69.7 %La Crosse County69.7Waukesha County: 68.7 %Waukesha County68.7Eau Claire County: 61.9 %Eau Claire County61.9Milwaukee County: 61.6 %Milwaukee County61.6Dodge County: 59 %Dodge County59Kenosha County: 58.6 %Kenosha County58.6Brown County: 56.7 %Brown County56.7Grant County: 55.8 %Grant County55.8Dane County: 33.1 %Dane County33.1Chippewa County: 100 %Chippewa County100Marathon County: 93.8 %Marathon County93.8Ashland County: 92.8 %Ashland County92.8Florence County: 92.1 %Florence County92.1Fond du Lac County: 91.8 %Fond du Lac County91.8Washington County: 90.7 %Washington County90.7Forest County: 90.6 %Forest County90.6Oneida County: 90.5 %Oneida County90.5Vernon County: 89.8 %Vernon County89.8Vilas County: 89.1 %Vilas County89.1Columbia County: 88.8 %Columbia County88.8Taylor County: 88.7 %Taylor County88.7Jefferson County: 86.6 %Jefferson County86.6Rock County: 85.5 %Rock County85.5Door County: 85.2 %Door County85.2Kewaunee County: 84.5 %Kewaunee County84.5Walworth County: 84.2 %Walworth County84.2Outagamie County: 79.7 %Outagamie County79.7Sauk County: 78.9 %Sauk County78.9Manitowoc County: 78.4 %Manitowoc County78.4Sheboygan County: 77.2 %Sheboygan County77.2St. Croix County: 76.5 %St. Croix County76.5Racine County: 75 %Racine County75Ozaukee County: 72.3 %Ozaukee County72.3La Crosse County: 69.7 %La Crosse County69.7Waukesha County: 68.7 %Waukesha County68.7Eau Claire County: 61.9 %Eau Claire County61.9Milwaukee County: 61.6 %Milwaukee County61.6Dodge County: 59 %Dodge County59Kenosha County: 58.6 %Kenosha County58.6Brown County: 56.7 %Brown County56.7Grant County: 55.8 %Grant County55.8Dane County: 33.1 %Dane County33.1
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2010 (%)Change on 2009
1Chippewa County100n/a
2Marathon County93.8+1.6 pts
3Ashland County92.8-1.7 pts
4Florence County92.1-4.4 pts
5Fond du Lac County91.8+4.7 pts
6Washington County90.7+1.6 pts
7Forest County90.6-3 pts
8Oneida County90.5-1.9 pts
9Vernon County89.8-1.2 pts
10Vilas County89.1+3.5 pts
11Columbia County88.8+1 pts
12Taylor County88.7+3.7 pts
13Jefferson County86.6+3.8 pts
14Rock County85.5+0.6 pts
15Door County85.2-1.3 pts
16Kewaunee County84.5-2.1 pts
17Walworth County84.2+4.6 pts
18Outagamie County79.7+23.5 pts
19Sauk County78.9-0.7 pts
20Manitowoc County78.4+1.5 pts
21Sheboygan County77.2-8.4 pts
22St. Croix County76.5-1.8 pts
23Racine County75-12 pts
24Ozaukee County72.3-1.5 pts
25La Crosse County69.7-10.4 pts
26Waukesha County68.7-3.9 pts
27Eau Claire County61.9-17.6 pts
28Milwaukee County61.6-11.8 pts
29Dodge County59-19.2 pts
30Kenosha County58.6-11.8 pts
31Brown County56.7+2.4 pts
32Grant County55.8+4.2 pts
33Dane County33.1-17.9 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. 15 counties with data in other periods have no value for 2010 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), 2010) [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), 2010. 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=2010. 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), 2010. 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=2010.

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), 2010 [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=2010 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_wisconsin_by_2010,
  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), 2010}},
  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=2010. 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), 2010
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=2010
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/wisconsin-counties?period=2010.
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)?

Chippewa County, with 100% in 2010, according to EPA.

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

Dane County, with 33.1% in 2010.

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. 15 counties have no value for 2010 and are not ranked.

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

Counties in Wisconsin: more rankings