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)

Taylor County had the highest share of days with good air quality (US EPA AQI) of 32 counties in 2000, at 90.4%. Milwaukee County had the lowest, at 30.1%. The median was 74.5%. Source: EPA.

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Highest90.4Taylor County
Lowest30.1Milwaukee County
Median74.532 counties

Map of counties, 2000

Brown County: 68.8 %Columbia County: 81.5 %Dane County: 74.6 %Dodge County: 71.5 %Door County: 75.7 %Douglas County: 68 %Florence County: 84.4 %Fond du Lac County: 83.9 %Grant County: 54.9 %Green County: 79.2 %Jefferson County: 49.3 %Kenosha County: 57.4 %Kewaunee County: 86.4 %Manitowoc County: 66.9 %Marathon County: 83.3 %Milwaukee County: 30.1 %Oneida County: 87 %Outagamie County: 74.4 %Ozaukee County: 63.3 %Racine County: 88.7 %Rock County: 46.9 %St. Croix County: 74.2 %Sauk County: 75.4 %Sheboygan County: 77.7 %Taylor County: 90.4 %Vernon County: 84.5 %Vilas County: 87.6 %Walworth County: 72.8 %Washington County: 84.6 %Waukesha County: 35.2 %Winnebago County: 72.3 %Wood County: 55.7 %
  • Under 56
  • 56 to 70
  • 70 to 75
  • 75 to 81
  • 81 to 85
  • 85 and over
  • No data
%, 2000. 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, 2000

Taylor County: 90.4 %Taylor County90.4Racine County: 88.7 %Racine County88.7Vilas County: 87.6 %Vilas County87.6Oneida County: 87 %Oneida County87Kewaunee County: 86.4 %Kewaunee County86.4Washington County: 84.6 %Washington County84.6Vernon County: 84.5 %Vernon County84.5Florence County: 84.4 %Florence County84.4Fond du Lac County: 83.9 %Fond du Lac County83.9Marathon County: 83.3 %Marathon County83.3Columbia County: 81.5 %Columbia County81.5Green County: 79.2 %Green County79.2Sheboygan County: 77.7 %Sheboygan County77.7Door County: 75.7 %Door County75.7Sauk County: 75.4 %Sauk County75.4Dane County: 74.6 %Dane County74.6Outagamie County: 74.4 %Outagamie County74.4St. Croix County: 74.2 %St. Croix County74.2Walworth County: 72.8 %Walworth County72.8Winnebago County: 72.3 %Winnebago County72.3Dodge County: 71.5 %Dodge County71.5Brown County: 68.8 %Brown County68.8Douglas County: 68 %Douglas County68Manitowoc County: 66.9 %Manitowoc County66.9Ozaukee County: 63.3 %Ozaukee County63.3Kenosha County: 57.4 %Kenosha County57.4Wood County: 55.7 %Wood County55.7Grant County: 54.9 %Grant County54.9Jefferson County: 49.3 %Jefferson County49.3Rock County: 46.9 %Rock County46.9Waukesha County: 35.2 %Waukesha County35.2Milwaukee County: 30.1 %Milwaukee County30.1Taylor County: 90.4 %Taylor County90.4Racine County: 88.7 %Racine County88.7Vilas County: 87.6 %Vilas County87.6Oneida County: 87 %Oneida County87Kewaunee County: 86.4 %Kewaunee County86.4Washington County: 84.6 %Washington County84.6Vernon County: 84.5 %Vernon County84.5Florence County: 84.4 %Florence County84.4Fond du Lac County: 83.9 %Fond du Lac County83.9Marathon County: 83.3 %Marathon County83.3Columbia County: 81.5 %Columbia County81.5Green County: 79.2 %Green County79.2Sheboygan County: 77.7 %Sheboygan County77.7Door County: 75.7 %Door County75.7Sauk County: 75.4 %Sauk County75.4Dane County: 74.6 %Dane County74.6Outagamie County: 74.4 %Outagamie County74.4St. Croix County: 74.2 %St. Croix County74.2Walworth County: 72.8 %Walworth County72.8Winnebago County: 72.3 %Winnebago County72.3Dodge County: 71.5 %Dodge County71.5Brown County: 68.8 %Brown County68.8Douglas County: 68 %Douglas County68Manitowoc County: 66.9 %Manitowoc County66.9Ozaukee County: 63.3 %Ozaukee County63.3Kenosha County: 57.4 %Kenosha County57.4Wood County: 55.7 %Wood County55.7Grant County: 54.9 %Grant County54.9Jefferson County: 49.3 %Jefferson County49.3Rock County: 46.9 %Rock County46.9Waukesha County: 35.2 %Waukesha County35.2Milwaukee County: 30.1 %Milwaukee County30.1
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2000 (%)Change on 1999
1Taylor County90.4+6.1 pts
2Racine County88.7+4.1 pts
3Vilas County87.6+3.7 pts
4Oneida County87+4.8 pts
5Kewaunee County86.4+15.4 pts
6Washington County84.6+16.1 pts
7Vernon County84.5+7.2 pts
8Florence County84.4+2.5 pts
9Fond du Lac County83.9+13.2 pts
10Marathon County83.3+8.5 pts
11Columbia County81.5+11 pts
12Green County79.2n/a
13Sheboygan County77.7+8.6 pts
14Door County75.7+5.1 pts
15Sauk County75.4-2.6 pts
16Dane County74.6+13.7 pts
17Outagamie County74.4+11.5 pts
18St. Croix County74.2+2.1 pts
19Walworth County72.8+10.6 pts
20Winnebago County72.3+14.7 pts
21Dodge County71.5+14.1 pts
22Brown County68.8+8.1 pts
23Douglas County68-2.5 pts
24Manitowoc County66.9+4 pts
25Ozaukee County63.3+8.9 pts
26Kenosha County57.4+5.9 pts
27Wood County55.7+6.6 pts
28Grant County54.9+19.8 pts
29Jefferson County49.3+3.7 pts
30Rock County46.9+0.8 pts
31Waukesha County35.2-30.8 pts
32Milwaukee County30.1+2.4 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. 16 counties with data in other periods have no value for 2000 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), 2000) [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), 2000. 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=2000. 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), 2000. 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=2000.

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), 2000 [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=2000 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_wisconsin_by_2000,
  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), 2000}},
  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=2000. 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), 2000
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=2000
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/wisconsin-counties?period=2000.
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)?

Taylor County, with 90.4% in 2000, according to EPA.

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

Milwaukee County, with 30.1% in 2000.

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. 16 counties have no value for 2000 and are not ranked.

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

Counties in Wisconsin: more rankings