Counties in Wisconsin by highest daily Air Quality Index (US EPA)

Manitowoc County had the highest highest daily Air Quality Index (US EPA) of 33 counties in 2010, at 174. Chippewa County had the lowest, at 21. The median was 108. Source: the U.S. Environmental Protection Agency.

Highest174Manitowoc County

Lowest21Chippewa County

Median10833 counties

Map of counties, 2010

Under 93
93 to 99
99 to 110
110 to 120
120 to 160
160 and over
No data

index, 2010. Hatched areas have no value for this period. Source: EPA, EPA AirData annual AQI by county: highest daily AQI. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2010

index. Source: EPA, EPA AirData annual AQI by county: highest daily AQI. Retrieved 2026-10-12.

Full ranking

Rank	Counties	2010 index	Change on 2009
1	Manitowoc County	174	+18
2	Door County	172	+22
3	Milwaukee County	166	-6
3	Sheboygan County	166	-8
5	Ozaukee County	161	-3
6	Kenosha County	159	+8
6	Kewaunee County	159	+19
8	Racine County	147	-14
9	Brown County	127	-4
10	Dane County	125	+14
10	Dodge County	125	+18
12	Grant County	124	-18
12	St. Croix County	124	-6
14	Waukesha County	119	-4
15	Sauk County	111	-4
16	La Crosse County	110	-11
17	Jefferson County	108	-4
17	Outagamie County	108	-5
19	Taylor County	103	+9
20	Fond du Lac County	101	+4
20	Rock County	101	+8
22	Walworth County	100	-19
23	Vilas County	97	+13
23	Washington County	97	-4
25	Eau Claire County	94	+18
26	Columbia County	93	+6
26	Florence County	93	+13
26	Forest County	93	+3
26	Oneida County	93	+3
26	Vernon County	93	+9
31	Marathon County	80	-7
32	Ashland County	71	-6
33	Chippewa County	21	n/a

Other periods

About this ranking

Highest daily Air Quality Index (AQI) value recorded in a US county during the year, from the EPA AirData annual summaries. Values above 500 are beyond the AQI scale and are published as EPA computes them.

A single day decides the value, so one wildfire or dust event can set it. Dust from the dry Owens Lake bed puts Inyo and Mono counties in California in the thousands. 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: highest daily AQI. 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: highest daily AQI (Counties in Wisconsin by highest daily Air Quality Index (US EPA), 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: highest daily AQI, Counties in Wisconsin by highest daily Air Quality Index (US EPA), 2010. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/wisconsin-counties?period=2010. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: highest daily AQI. Counties in Wisconsin by highest daily Air Quality Index (US EPA), 2010. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/wisconsin-counties?period=2010.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: highest daily AQI, Counties in Wisconsin by highest daily Air Quality Index (US EPA), 2010 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/highest-daily-air-quality-index/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: highest daily AQI: Counties in Wisconsin by highest daily Air Quality Index (US EPA), 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/highest-daily-air-quality-index/wisconsin-counties?period=2010. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest daily AQI. 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: highest daily AQI: Counties in Wisconsin by highest daily Air Quality Index (US EPA), 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/highest-daily-air-quality-index/wisconsin-counties?period=2010
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/wisconsin-counties?period=2010.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest daily AQI. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
ER  -

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Rank Counties in Wisconsin by highest daily Air Quality Index (US EPA) using official data, and cite the source.

rank_places {"indicator":"aqi_max","level":"province","within":"Wisconsin","limit":10}
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Questions

Which county has the highest highest daily Air Quality Index (US EPA)?

Manitowoc County, with 174 in 2010, according to the U.S. Environmental Protection Agency.

Which county has the lowest highest daily Air Quality Index (US EPA)?

Chippewa County, with 21 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: highest daily AQI. Retrieved 2026-10-12. 15 counties have no value for 2010 and are not ranked.