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

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

Highest daily Air Quality Index (US EPA) in Madison County was 64 in 1999, according to the U.S. Environmental Protection Agency. That is down 11 from 1998.

1999, index64
Change on 1998-11
Series high751998
Series low391994

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 Madison County, 1994 to 1999

3040506070801994199519961997199819991994: 39 index1995: 63 index1996: 60 index1997: 43 index1998: 75 index1999: 64 index3040506070801994199619991994: 39 index1995: 63 index1996: 60 index1997: 43 index1998: 75 index1999: 64 index
index. Source: EPA, EPA AirData annual AQI by county: highest daily AQI. Retrieved 2026-10-12, published 2026-07-13.
All 6 values
Periodindex
199964
199875
199743
199660
199563
199439

Madison County compared with nearby places

Ada County: 149 indexBannock County: 195 indexBlaine County: 56 indexBonner County: 101 indexBonneville County: 115 indexBoundary County: 46 indexButte County: 112 indexCanyon County: 151 indexCaribou County: 68 indexCuster County: 58 indexKootenai County: 167 indexLemhi County: 79 indexLewis County: 67 indexMadison County: 64 indexMinidoka County: 73 indexNez Perce County: 111 indexPower County: 488 indexShoshone County: 162 indexTwin Falls County: 102 index
  • Under 66
  • 66 to 83
  • 83 to 110
  • 110 to 160
  • 160 and over
  • No data
Highest daily Air Quality Index (US EPA), 1999, index. Madison 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), Madison County, 1994 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), Madison County, 1994 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/madison-county-idaho. 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), Madison County, 1994 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/madison-county-idaho.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: highest daily AQI, Highest daily Air Quality Index (US EPA), Madison County, 1994 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/madison-county-idaho (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), Madison County, 1994 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/madison-county-idaho. 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), Madison County, 1994 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/madison-county-idaho
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/en/highest-daily-air-quality-index/madison-county-idaho.
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 Madison County?

Highest daily Air Quality Index (US EPA) in Madison County was 64 in 1999, according to the U.S. Environmental Protection Agency. That is down 11 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 Madison County?

75 in 1998, the highest value since 1994 in this series.

Related statistics for Madison County

All statistics for Madison County | Madison County in figures