Data / Highest daily Air Quality Index (US EPA) / Polk County

Highest daily Air Quality Index (US EPA) in Polk County

Highest daily Air Quality Index (US EPA) in Polk County was 9 in 1999, according to the U.S. Environmental Protection Agency. That is down 147 from 1998.

1999, index9
Change on 1998-147
Series high1561998
Series low91999

Next release: Tuesday, 13 July 2027, estimated by Invokely from past publication dates (low confidence), not announced by the publisher. Release calendar

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Highest daily Air Quality Index (US EPA) in Polk County, 1991 to 1999

050100150200199119931995199719991991: 80 index1992: 108 index1993: 90 index1994: 119 index1995: 133 index1996: 115 index1997: 119 index1998: 156 index1999: 9 index0501001502001991199419991991: 80 index1992: 108 index1993: 90 index1994: 119 index1995: 133 index1996: 115 index1997: 119 index1998: 156 index1999: 9 index
index. Source: EPA, EPA AirData annual AQI by county: highest daily AQI. Retrieved 2026-10-12, published 2026-07-13.
All 9 values
Periodindex
19999
1998156
1997119
1996115
1995133
1994119
199390
1992108
199180

Polk County compared with nearby places

Brown County: 172 indexColumbia County: 172 indexDane County: 174 indexDodge County: 172 indexDoor County: 208 indexDouglas County: 90 indexFlorence County: 161 indexFond du Lac County: 179 indexGrant County: 115 indexJefferson County: 195 indexKenosha County: 195 indexKewaunee County: 192 indexManitowoc County: 190 indexMarathon County: 166 indexMilwaukee County: 197 indexOneida County: 161 indexOutagamie County: 182 indexOzaukee County: 192 indexPolk County: 9 indexRacine County: 185 indexRock County: 179 indexSt. Croix County: 133 indexSauk County: 185 indexSheboygan County: 200 indexTaylor County: 177 indexVernon County: 174 indexVilas County: 154 indexWalworth County: 205 indexWashington County: 177 indexWaukesha County: 192 indexWinnebago County: 169 indexWood County: 111 index
  • Under 160
  • 160 to 170
  • 170 to 180
  • 180 to 190
  • 190 and over
  • No data
Highest daily Air Quality Index (US EPA), 1999, index. Polk County is outlined. Same source and period for every area shown. Source: U.S. Environmental Protection Agency. Boundaries: U.S. Census Bureau cartographic boundary files.

Rankings

Definition

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.

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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 (Highest daily Air Quality Index (US EPA), Polk County, 1991 to 1999) [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, Highest daily Air Quality Index (US EPA), Polk County, 1991 to 1999. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/en/highest-daily-air-quality-index/polk-county-wisconsin. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: highest daily AQI. Highest daily Air Quality Index (US EPA), Polk County, 1991 to 1999. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/en/highest-daily-air-quality-index/polk-county-wisconsin.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: highest daily AQI, Highest daily Air Quality Index (US EPA), Polk County, 1991 to 1999 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/en/highest-daily-air-quality-index/polk-county-wisconsin (Accessed: 12 October 2026).

BibTeX
@misc{environmental_highest_daily_air_quality_1999,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: highest daily AQI: Highest daily Air Quality Index (US EPA), Polk County, 1991 to 1999}},
  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/en/highest-daily-air-quality-index/polk-county-wisconsin. 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: Highest daily Air Quality Index (US EPA), Polk County, 1991 to 1999
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/en/highest-daily-air-quality-index/polk-county-wisconsin
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/en/highest-daily-air-quality-index/polk-county-wisconsin.
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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Questions

What is the highest daily Air Quality Index (US EPA) in Polk County?

Highest daily Air Quality Index (US EPA) in Polk County was 9 in 1999, according to the U.S. Environmental Protection Agency. That is down 147 from 1998.

Where does this figure come from?

U.S. Environmental Protection Agency. EPA AirData annual AQI by county: highest daily AQI. Retrieved by Invokely on 2026-10-12.

What was the highest highest daily Air Quality Index (US EPA) in Polk County?

156 in 1998, the highest value since 1991 in this series.

Related statistics for Polk County

All statistics for Polk County | Polk County in figures