Data / Rankings / Share of days with good air quality (US EPA AQI) / Counties in Idaho

Counties in Idaho by share of days with good air quality (US EPA AQI)

Lewis County had the highest share of days with good air quality (US EPA AQI) of 24 counties in 2002, at 100%. Idaho County had the lowest, at 25%. The median was 75.2%. Source: EPA.

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Highest100Lewis County
Lowest25Idaho County
Median75.224 counties

Map of counties, 2002

Ada County: 61.4 %Bannock County: 81.7 %Benewah County: 94 %Bingham County: 90.4 %Boise County: 47.6 %Bonner County: 94.2 %Bonneville County: 66.7 %Boundary County: 74.3 %Butte County: 66.1 %Canyon County: 66.3 %Caribou County: 97.9 %Custer County: 99 %Elmore County: 68.2 %Idaho County: 25 %Kootenai County: 59.7 %Latah County: 74.2 %Lemhi County: 90 %Lewis County: 100 %Minidoka County: 100 %Nez Perce County: 83.7 %Power County: 48.7 %Shoshone County: 83.5 %Twin Falls County: 76 %Valley County: 53.3 %
  • Under 61
  • 61 to 69
  • 69 to 83
  • 83 to 94
  • 94 and over
  • No data
%, 2002. 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, 2002

Lewis County: 100 %Lewis County100Minidoka County: 100 %Minidoka County100Custer County: 99 %Custer County99Caribou County: 97.9 %Caribou County97.9Bonner County: 94.2 %Bonner County94.2Benewah County: 94 %Benewah County94Bingham County: 90.4 %Bingham County90.4Lemhi County: 90 %Lemhi County90Nez Perce County: 83.7 %Nez Perce County83.7Shoshone County: 83.5 %Shoshone County83.5Bannock County: 81.7 %Bannock County81.7Twin Falls County: 76 %Twin Falls County76Boundary County: 74.3 %Boundary County74.3Latah County: 74.2 %Latah County74.2Elmore County: 68.2 %Elmore County68.2Bonneville County: 66.7 %Bonneville County66.7Canyon County: 66.3 %Canyon County66.3Butte County: 66.1 %Butte County66.1Ada County: 61.4 %Ada County61.4Kootenai County: 59.7 %Kootenai County59.7Valley County: 53.3 %Valley County53.3Power County: 48.7 %Power County48.7Boise County: 47.6 %Boise County47.6Idaho County: 25 %Idaho County25Lewis County: 100 %Lewis County100Minidoka County: 100 %Minidoka County100Custer County: 99 %Custer County99Caribou County: 97.9 %Caribou County97.9Bonner County: 94.2 %Bonner County94.2Benewah County: 94 %Benewah County94Bingham County: 90.4 %Bingham County90.4Lemhi County: 90 %Lemhi County90Nez Perce County: 83.7 %Nez Perce County83.7Shoshone County: 83.5 %Shoshone County83.5Bannock County: 81.7 %Bannock County81.7Twin Falls County: 76 %Twin Falls County76Boundary County: 74.3 %Boundary County74.3Latah County: 74.2 %Latah County74.2Elmore County: 68.2 %Elmore County68.2Bonneville County: 66.7 %Bonneville County66.7Canyon County: 66.3 %Canyon County66.3Butte County: 66.1 %Butte County66.1Ada County: 61.4 %Ada County61.4Kootenai County: 59.7 %Kootenai County59.7Valley County: 53.3 %Valley County53.3Power County: 48.7 %Power County48.7Boise County: 47.6 %Boise County47.6Idaho County: 25 %Idaho County25
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2002 (%)Change on 2001
1Lewis County100+3.4 pts
1Minidoka County100+8.3 pts
3Custer County99-0.1 pts
4Caribou County97.9-2.1 pts
5Bonner County94.2+7.7 pts
6Benewah County94-0.3 pts
7Bingham County90.4-1.4 pts
8Lemhi County90+5.4 pts
9Nez Perce County83.7-3.9 pts
10Shoshone County83.5+0.9 pts
11Bannock County81.7+13.9 pts
12Twin Falls County76-6.2 pts
13Boundary County74.3n/a
14Latah County74.2n/a
15Elmore County68.2-7 pts
16Bonneville County66.7-11.6 pts
17Canyon County66.3-14.5 pts
18Butte County66.1-31.8 pts
19Ada County61.4-0.5 pts
20Kootenai County59.7-26.2 pts
21Valley County53.3n/a
22Power County48.7+26.7 pts
23Boise County47.6n/a
24Idaho County25n/a

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. 7 counties with data in other periods have no value for 2002 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 Idaho by share of days with good air quality (US EPA AQI), 2002) [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 Idaho by share of days with good air quality (US EPA AQI), 2002. 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/idaho-counties?period=2002. 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 Idaho by share of days with good air quality (US EPA AQI), 2002. 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/idaho-counties?period=2002.

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 Idaho by share of days with good air quality (US EPA AQI), 2002 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/good-air-quality-days-share/idaho-counties?period=2002 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_idaho_by_2002,
  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 Idaho by share of days with good air quality (US EPA AQI), 2002}},
  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/idaho-counties?period=2002. 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 Idaho by share of days with good air quality (US EPA AQI), 2002
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/idaho-counties?period=2002
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/idaho-counties?period=2002.
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)?

Lewis County, with 100% in 2002, according to EPA.

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

Idaho County, with 25% in 2002.

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. 7 counties have no value for 2002 and are not ranked.

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

Counties in Idaho: more rankings