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)

Bonner County had the highest share of days with good air quality (US EPA AQI) of 24 counties in 2004, at 98%. Gem County had the lowest, at 14.3%. The median was 77.6%. Source: EPA.

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Highest98Bonner County
Lowest14.3Gem County
Median77.624 counties

Map of counties, 2004

Ada County: 64.2 %Bannock County: 94 %Benewah County: 57.9 %Bingham County: 94.3 %Boise County: 77.5 %Bonner County: 98 %Bonneville County: 65.5 %Boundary County: 86.5 %Butte County: 85.4 %Canyon County: 65.3 %Caribou County: 75 %Custer County: 97.4 %Elmore County: 80.7 %Franklin County: 50 %Gem County: 14.3 %Idaho County: 86.3 %Kootenai County: 48.2 %Latah County: 84.9 %Lemhi County: 72.1 %Nez Perce County: 79.3 %Power County: 52.1 %Shoshone County: 54.1 %Twin Falls County: 79.7 %Valley County: 77.6 %
  • Under 56
  • 56 to 73
  • 73 to 80
  • 80 to 86
  • 86 and over
  • No data
%, 2004. 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, 2004

Bonner County: 98 %Bonner County98Custer County: 97.4 %Custer County97.4Bingham County: 94.3 %Bingham County94.3Bannock County: 94 %Bannock County94Boundary County: 86.5 %Boundary County86.5Idaho County: 86.3 %Idaho County86.3Butte County: 85.4 %Butte County85.4Latah County: 84.9 %Latah County84.9Elmore County: 80.7 %Elmore County80.7Twin Falls County: 79.7 %Twin Falls County79.7Nez Perce County: 79.3 %Nez Perce County79.3Valley County: 77.6 %Valley County77.6Boise County: 77.5 %Boise County77.5Caribou County: 75 %Caribou County75Lemhi County: 72.1 %Lemhi County72.1Bonneville County: 65.5 %Bonneville County65.5Canyon County: 65.3 %Canyon County65.3Ada County: 64.2 %Ada County64.2Benewah County: 57.9 %Benewah County57.9Shoshone County: 54.1 %Shoshone County54.1Power County: 52.1 %Power County52.1Franklin County: 50 %Franklin County50Kootenai County: 48.2 %Kootenai County48.2Gem County: 14.3 %Gem County14.3Bonner County: 98 %Bonner County98Custer County: 97.4 %Custer County97.4Bingham County: 94.3 %Bingham County94.3Bannock County: 94 %Bannock County94Boundary County: 86.5 %Boundary County86.5Idaho County: 86.3 %Idaho County86.3Butte County: 85.4 %Butte County85.4Latah County: 84.9 %Latah County84.9Elmore County: 80.7 %Elmore County80.7Twin Falls County: 79.7 %Twin Falls County79.7Nez Perce County: 79.3 %Nez Perce County79.3Valley County: 77.6 %Valley County77.6Boise County: 77.5 %Boise County77.5Caribou County: 75 %Caribou County75Lemhi County: 72.1 %Lemhi County72.1Bonneville County: 65.5 %Bonneville County65.5Canyon County: 65.3 %Canyon County65.3Ada County: 64.2 %Ada County64.2Benewah County: 57.9 %Benewah County57.9Shoshone County: 54.1 %Shoshone County54.1Power County: 52.1 %Power County52.1Franklin County: 50 %Franklin County50Kootenai County: 48.2 %Kootenai County48.2Gem County: 14.3 %Gem County14.3
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2004 (%)Change on 2003
1Bonner County98+1.8 pts
2Custer County97.4-1.7 pts
3Bingham County94.3+18.3 pts
4Bannock County94-2.3 pts
5Boundary County86.5-6.7 pts
6Idaho County86.3+29.2 pts
7Butte County85.4+10.5 pts
8Latah County84.9-15.1 pts
9Elmore County80.7-5.3 pts
10Twin Falls County79.7-1.3 pts
11Nez Perce County79.3+8.1 pts
12Valley County77.6-7.8 pts
13Boise County77.5+5.1 pts
14Caribou County75-19.1 pts
15Lemhi County72.1-21.3 pts
16Bonneville County65.5-20.7 pts
17Canyon County65.3-7.9 pts
18Ada County64.2-10.1 pts
19Benewah County57.9-16.3 pts
20Shoshone County54.1-31.3 pts
21Power County52.1-5.5 pts
22Franklin County50n/a
23Kootenai County48.2-17.5 pts
24Gem County14.3n/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 2004 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), 2004) [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), 2004. 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=2004. 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), 2004. 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=2004.

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), 2004 [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=2004 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_idaho_by_2004,
  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), 2004}},
  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=2004. 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), 2004
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=2004
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/idaho-counties?period=2004.
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)?

Bonner County, with 98% in 2004, according to EPA.

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

Gem County, with 14.3% in 2004.

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 2004 and are not ranked.

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

Counties in Idaho: more rankings