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)

Florence County had the highest share of days with good air quality (US EPA AQI) of 32 counties in 2009, at 96.5%. Dane County had the lowest, at 51%. The median was 83.9%. Source: EPA.

Keep it in a collection in your library.
Highest96.5Florence County
Lowest51Dane County
Median83.932 counties

Map of counties, 2009

Ashland County: 94.5 %Brown County: 54.3 %Columbia County: 87.8 %Dane County: 51 %Dodge County: 78.2 %Door County: 86.5 %Eau Claire County: 79.5 %Florence County: 96.5 %Fond du Lac County: 87.1 %Forest County: 93.6 %Grant County: 51.6 %Jefferson County: 82.8 %Kenosha County: 70.4 %Kewaunee County: 86.6 %La Crosse County: 80.1 %Manitowoc County: 76.9 %Marathon County: 92.2 %Milwaukee County: 73.4 %Oneida County: 92.4 %Outagamie County: 56.2 %Ozaukee County: 73.8 %Racine County: 87 %Rock County: 84.9 %St. Croix County: 78.3 %Sauk County: 79.6 %Sheboygan County: 85.6 %Taylor County: 85 %Vernon County: 91 %Vilas County: 85.6 %Walworth County: 79.6 %Washington County: 89.1 %Waukesha County: 72.6 %
  • Under 73
  • 73 to 79
  • 79 to 84
  • 84 to 87
  • 87 to 91
  • 91 and over
  • No data
%, 2009. 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, 2009

Florence County: 96.5 %Florence County96.5Ashland County: 94.5 %Ashland County94.5Forest County: 93.6 %Forest County93.6Oneida County: 92.4 %Oneida County92.4Marathon County: 92.2 %Marathon County92.2Vernon County: 91 %Vernon County91Washington County: 89.1 %Washington County89.1Columbia County: 87.8 %Columbia County87.8Fond du Lac County: 87.1 %Fond du Lac County87.1Racine County: 87 %Racine County87Kewaunee County: 86.6 %Kewaunee County86.6Door County: 86.5 %Door County86.5Sheboygan County: 85.6 %Sheboygan County85.6Vilas County: 85.6 %Vilas County85.6Taylor County: 85 %Taylor County85Rock County: 84.9 %Rock County84.9Jefferson County: 82.8 %Jefferson County82.8La Crosse County: 80.1 %La Crosse County80.1Sauk County: 79.6 %Sauk County79.6Walworth County: 79.6 %Walworth County79.6Eau Claire County: 79.5 %Eau Claire County79.5St. Croix County: 78.3 %St. Croix County78.3Dodge County: 78.2 %Dodge County78.2Manitowoc County: 76.9 %Manitowoc County76.9Ozaukee County: 73.8 %Ozaukee County73.8Milwaukee County: 73.4 %Milwaukee County73.4Waukesha County: 72.6 %Waukesha County72.6Kenosha County: 70.4 %Kenosha County70.4Outagamie County: 56.2 %Outagamie County56.2Brown County: 54.3 %Brown County54.3Grant County: 51.6 %Grant County51.6Dane County: 51 %Dane County51Florence County: 96.5 %Florence County96.5Ashland County: 94.5 %Ashland County94.5Forest County: 93.6 %Forest County93.6Oneida County: 92.4 %Oneida County92.4Marathon County: 92.2 %Marathon County92.2Vernon County: 91 %Vernon County91Washington County: 89.1 %Washington County89.1Columbia County: 87.8 %Columbia County87.8Fond du Lac County: 87.1 %Fond du Lac County87.1Racine County: 87 %Racine County87Kewaunee County: 86.6 %Kewaunee County86.6Door County: 86.5 %Door County86.5Sheboygan County: 85.6 %Sheboygan County85.6Vilas County: 85.6 %Vilas County85.6Taylor County: 85 %Taylor County85Rock County: 84.9 %Rock County84.9Jefferson County: 82.8 %Jefferson County82.8La Crosse County: 80.1 %La Crosse County80.1Sauk County: 79.6 %Sauk County79.6Walworth County: 79.6 %Walworth County79.6Eau Claire County: 79.5 %Eau Claire County79.5St. Croix County: 78.3 %St. Croix County78.3Dodge County: 78.2 %Dodge County78.2Manitowoc County: 76.9 %Manitowoc County76.9Ozaukee County: 73.8 %Ozaukee County73.8Milwaukee County: 73.4 %Milwaukee County73.4Waukesha County: 72.6 %Waukesha County72.6Kenosha County: 70.4 %Kenosha County70.4Outagamie County: 56.2 %Outagamie County56.2Brown County: 54.3 %Brown County54.3Grant County: 51.6 %Grant County51.6Dane County: 51 %Dane County51
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2009 (%)Change on 2008
1Florence County96.5+6.6 pts
2Ashland County94.5+0.3 pts
3Forest County93.6+6.3 pts
4Oneida County92.4+5.2 pts
5Marathon County92.2+2.9 pts
6Vernon County91+1 pts
7Washington County89.1-3.5 pts
8Columbia County87.8+4.1 pts
9Fond du Lac County87.1-0.7 pts
10Racine County87+1.8 pts
11Kewaunee County86.6+0.7 pts
12Door County86.5+3.3 pts
13Sheboygan County85.6+6.8 pts
13Vilas County85.6-0.4 pts
15Taylor County85+5.1 pts
16Rock County84.9+4.5 pts
17Jefferson County82.8-0.2 pts
18La Crosse County80.1+6.6 pts
19Sauk County79.6+1.8 pts
19Walworth County79.60 pts
21Eau Claire County79.5n/a
22St. Croix County78.3+1.3 pts
23Dodge County78.2+4.7 pts
24Manitowoc County76.9+9.5 pts
25Ozaukee County73.8+9.3 pts
26Milwaukee County73.4+8.1 pts
27Waukesha County72.6+0.5 pts
28Kenosha County70.4+10.2 pts
29Outagamie County56.2-12.6 pts
30Brown County54.3+10 pts
31Grant County51.6+18 pts
32Dane County51+10.2 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 2009 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), 2009) [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), 2009. 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=2009. 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), 2009. 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=2009.

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), 2009 [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=2009 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_wisconsin_by_2009,
  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), 2009}},
  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=2009. 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), 2009
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=2009
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/wisconsin-counties?period=2009.
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  -
Embed this chart

Paste this code into a web page or a blog post. The chart shows the latest figures as they are published, with the source and a link back to this page.

Sites that read oEmbed links, such as WordPress, can show the chart when you paste the link to this page.

Use this data in your AI agent

Invokely serves this figure to AI assistants through MCP and to code through a REST API, with the source and citation attached. Ask your assistant:

Rank Counties in Wisconsin by share of days with good air quality (US EPA AQI) using official data, and cite the source.
rank_places {"indicator":"aqi_good_days_share","level":"province","within":"Wisconsin","limit":10}
GET https://invokely.ai/api/v1/rank?indicator=aqi_good_days_share&level=province&within=Wisconsin&limit=10

Connect Claude, ChatGPT or Cursor in one step. The trial answers 25 calls a day without an account.

Questions

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

Florence County, with 96.5% in 2009, according to EPA.

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

Dane County, with 51% in 2009.

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 2009 and are not ranked.

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

Counties in Wisconsin: more rankings