Counties in Idaho by share of days with good air quality (US EPA AQI), 2005

Butte County had the highest share of days with good air quality (US EPA AQI) of 23 counties in 2005, at 100%. Kootenai County had the lowest, at 49.9%. The median was 75.7%. Source: EPA.

Highest100Butte County

Lowest49.9Kootenai County

Median75.723 counties

All counties, 2005

%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

Rank	Counties	2005 (%)	Change on 2004
1	Butte County	100	+14.6 pts
2	Custer County	99.1	+1.7 pts
3	Bonneville County	97.5	+32 pts
4	Bonner County	96.5	-1.5 pts
5	Latah County	95.2	+10.3 pts
6	Bingham County	92.3	-2 pts
7	Nez Perce County	89.1	+9.8 pts
8	Idaho County	86.9	+0.6 pts
9	Boundary County	84.9	-1.6 pts
10	Bannock County	84.7	-9.3 pts
11	Twin Falls County	78.5	-1.2 pts
12	Benewah County	75.7	+17.8 pts
13	Franklin County	74.8	+24.8 pts
14	Elmore County	68.4	-12.3 pts
15	Valley County	65.9	-11.7 pts
16	Canyon County	64.9	-0.4 pts
17	Gem County	63.3	+49 pts
18	Lemhi County	62.1	-10 pts
19	Ada County	61.9	-2.3 pts
20	Boise County	57.9	-19.6 pts
21	Shoshone County	51.4	-2.7 pts
22	Power County	50.4	-1.7 pts
23	Kootenai County	49.9	+1.7 pts

Other periods

2005
2004
2003
2002

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. 8 counties with data in other periods have no value for 2005 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), 2005) [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), 2005. 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. 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), 2005. 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.

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), 2005 [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 (Accessed: 12 October 2026).

BibTeX

@misc{environmental_counties_in_idaho_by_2005,
  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), 2005}},
  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. 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), 2005
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
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/idaho-counties.
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)?

Butte County, with 100% in 2005, according to EPA.

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

Kootenai County, with 49.9% in 2005.

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. 8 counties have no value for 2005 and are not ranked.