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 2003, at 100%. Wood County had the lowest, at 41.7%. The median was 68.3%. Source: EPA.

Keep it in a collection in your library.
Highest100Eau Claire County
Lowest41.7Wood County
Median68.335 counties

Map of counties, 2003

Ashland County: 83.9 %Brown County: 63.7 %Columbia County: 62.5 %Dane County: 54.7 %Dodge County: 53.4 %Door County: 76.8 %Douglas County: 85.7 %Eau Claire County: 100 %Florence County: 83.1 %Fond du Lac County: 72.3 %Forest County: 98.2 %Grant County: 47.9 %Green County: 63.6 %Jefferson County: 61.8 %Kenosha County: 57.3 %Kewaunee County: 74.5 %Manitowoc County: 65 %Marathon County: 72.5 %Milwaukee County: 63.6 %Oneida County: 75.1 %Outagamie County: 68.3 %Ozaukee County: 64.8 %Racine County: 78 %Rock County: 61.8 %St. Croix County: 71.7 %Sauk County: 75.1 %Sheboygan County: 67.9 %Taylor County: 77.8 %Vernon County: 61.1 %Vilas County: 80.3 %Walworth County: 59.6 %Washington County: 74.5 %Waukesha County: 50.3 %Winnebago County: 69.2 %Wood County: 41.7 %
  • Under 59
  • 59 to 64
  • 64 to 68
  • 68 to 75
  • 75 to 79
  • 79 and over
  • No data
%, 2003. 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, 2003

Eau Claire County: 100 %Eau Claire County100Forest County: 98.2 %Forest County98.2Douglas County: 85.7 %Douglas County85.7Ashland County: 83.9 %Ashland County83.9Florence County: 83.1 %Florence County83.1Vilas County: 80.3 %Vilas County80.3Racine County: 78 %Racine County78Taylor County: 77.8 %Taylor County77.8Door County: 76.8 %Door County76.8Oneida County: 75.1 %Oneida County75.1Sauk County: 75.1 %Sauk County75.1Kewaunee County: 74.5 %Kewaunee County74.5Washington County: 74.5 %Washington County74.5Marathon County: 72.5 %Marathon County72.5Fond du Lac County: 72.3 %Fond du Lac County72.3St. Croix County: 71.7 %St. Croix County71.7Winnebago County: 69.2 %Winnebago County69.2Outagamie County: 68.3 %Outagamie County68.3Sheboygan County: 67.9 %Sheboygan County67.9Manitowoc County: 65 %Manitowoc County65Ozaukee County: 64.8 %Ozaukee County64.8Brown County: 63.7 %Brown County63.7Green County: 63.6 %Green County63.6Milwaukee County: 63.6 %Milwaukee County63.6Columbia County: 62.5 %Columbia County62.5Jefferson County: 61.8 %Jefferson County61.8Rock County: 61.8 %Rock County61.8Vernon County: 61.1 %Vernon County61.1Walworth County: 59.6 %Walworth County59.6Kenosha County: 57.3 %Kenosha County57.3Dane County: 54.7 %Dane County54.7Dodge County: 53.4 %Dodge County53.4Waukesha County: 50.3 %Waukesha County50.3Grant County: 47.9 %Grant County47.9Wood County: 41.7 %Wood County41.7Eau Claire County: 100 %Eau Claire County100Forest County: 98.2 %Forest County98.2Douglas County: 85.7 %Douglas County85.7Ashland County: 83.9 %Ashland County83.9Florence County: 83.1 %Florence County83.1Vilas County: 80.3 %Vilas County80.3Racine County: 78 %Racine County78Taylor County: 77.8 %Taylor County77.8Door County: 76.8 %Door County76.8Oneida County: 75.1 %Oneida County75.1Sauk County: 75.1 %Sauk County75.1Kewaunee County: 74.5 %Kewaunee County74.5Washington County: 74.5 %Washington County74.5Marathon County: 72.5 %Marathon County72.5Fond du Lac County: 72.3 %Fond du Lac County72.3St. Croix County: 71.7 %St. Croix County71.7Winnebago County: 69.2 %Winnebago County69.2Outagamie County: 68.3 %Outagamie County68.3Sheboygan County: 67.9 %Sheboygan County67.9Manitowoc County: 65 %Manitowoc County65Ozaukee County: 64.8 %Ozaukee County64.8Brown County: 63.7 %Brown County63.7Green County: 63.6 %Green County63.6Milwaukee County: 63.6 %Milwaukee County63.6Columbia County: 62.5 %Columbia County62.5Jefferson County: 61.8 %Jefferson County61.8Rock County: 61.8 %Rock County61.8Vernon County: 61.1 %Vernon County61.1Walworth County: 59.6 %Walworth County59.6Kenosha County: 57.3 %Kenosha County57.3Dane County: 54.7 %Dane County54.7Dodge County: 53.4 %Dodge County53.4Waukesha County: 50.3 %Waukesha County50.3Grant County: 47.9 %Grant County47.9Wood County: 41.7 %Wood County41.7
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2003 (%)Change on 2002
1Eau Claire County1000 pts
2Forest County98.2-1.8 pts
3Douglas County85.7+11.1 pts
4Ashland County83.9-9.2 pts
5Florence County83.1+0.7 pts
6Vilas County80.3-7 pts
7Racine County78-8 pts
8Taylor County77.8-4.8 pts
9Door County76.8+7.2 pts
10Oneida County75.1-10.1 pts
10Sauk County75.1-4.9 pts
12Kewaunee County74.5+4.6 pts
12Washington County74.5+9.7 pts
14Marathon County72.5-6.1 pts
15Fond du Lac County72.3+3.8 pts
16St. Croix County71.7-0.5 pts
17Winnebago County69.2+10.1 pts
18Outagamie County68.3+1.8 pts
19Sheboygan County67.9+4.3 pts
20Manitowoc County65+1.6 pts
21Ozaukee County64.8+3.3 pts
22Brown County63.7-0.6 pts
23Green County63.6-1.6 pts
23Milwaukee County63.6+12.1 pts
25Columbia County62.5-5.6 pts
26Jefferson County61.8+7.7 pts
26Rock County61.8+6.1 pts
28Vernon County61.1-13.2 pts
29Walworth County59.6+0.8 pts
30Kenosha County57.3+5.1 pts
31Dane County54.7+0.9 pts
32Dodge County53.4-6.5 pts
33Waukesha County50.3+4.8 pts
34Grant County47.9-0.4 pts
35Wood County41.7-7.5 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 2003 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), 2003) [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), 2003. 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=2003. 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), 2003. 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=2003.

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), 2003 [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=2003 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_wisconsin_by_2003,
  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), 2003}},
  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=2003. 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), 2003
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=2003
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/wisconsin-counties?period=2003.
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 2003, according to EPA.

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

Wood County, with 41.7% in 2003.

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 2003 and are not ranked.

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

Counties in Wisconsin: more rankings