Data / Median Air Quality Index (US EPA) / Walla Walla County

Median Air Quality Index (US EPA) in Walla Walla County

Median Air Quality Index (US EPA) in Walla Walla County was 28 in 2025, according to the U.S. Environmental Protection Agency. That is up 4 from 2024. That is the 15th highest of 31 counties in 2025.

2025, index28
Change on 2024+4
Rank15th of 31Counties in Washington ranked
Series high411986
Series low202000

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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Median Air Quality Index (US EPA) in Walla Walla County, 1986 to 2025

20253035404519861992199820042010201620251986: 41 index1987: 40 index1988: 36 index1989: 30 index1990: 33 index1991: 32 index1992: 27 index1993: 25 index1994: 27 index1995: 21 index1996: 26 index1997: 29 index1998: 23 index1999: 23 index2000: 20 index2001: 26 index2002: 34 index2003: 38 index2004: 41 index2005: 31 index2006: 35 index2007: 31 index2008: 33 index2009: 35 index2010: 29 index2011: 26 index2012: 24 index2013: 28 index2014: 22 index2015: 26 index2016: 24 index2017: 23 index2018: 26 index2019: 23 index2020: 26 index2021: 24 index2022: 25 index2023: 28 index2024: 24 index2025: 28 index2030405019862000201420251986: 41 index1987: 40 index1988: 36 index1989: 30 index1990: 33 index1991: 32 index1992: 27 index1993: 25 index1994: 27 index1995: 21 index1996: 26 index1997: 29 index1998: 23 index1999: 23 index2000: 20 index2001: 26 index2002: 34 index2003: 38 index2004: 41 index2005: 31 index2006: 35 index2007: 31 index2008: 33 index2009: 35 index2010: 29 index2011: 26 index2012: 24 index2013: 28 index2014: 22 index2015: 26 index2016: 24 index2017: 23 index2018: 26 index2019: 23 index2020: 26 index2021: 24 index2022: 25 index2023: 28 index2024: 24 index2025: 28 index
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12, published 2026-07-13.
All 40 values
Periodindex
202528
202424
202328
202225
202124
202026
201923
201826
201723
201624
201526
201422
201328
201224
201126
201029
200935
200833
200731
200635
200531
200441
200338
200234
200126
200020
199923
199823
199729
199626
199521
199427
199325
199227
199132
199033
198930
198836
198740
198641

Walla Walla County compared with nearby places

Adams County: 21 indexAsotin County: 42 indexBenton County: 36 indexChelan County: 35 indexClallam County: 29 indexClark County: 33 indexColumbia County: 36 indexCowlitz County: 22 indexFranklin County: 23 indexGarfield County: 19 indexGrant County: 28 indexGrays Harbor County: 22 indexJefferson County: 20 indexKing County: 43 indexKitsap County: 22 indexKittitas County: 25 indexKlickitat County: 23 indexLewis County: 20 indexMason County: 23 indexOkanogan County: 41 indexPacific County: 16 indexPierce County: 44 indexSkagit County: 25 indexSnohomish County: 41 indexSpokane County: 43 indexStevens County: 35 indexThurston County: 27 indexWalla Walla County: 28 indexWhatcom County: 31 indexWhitman County: 23 indexYakima County: 41 index
  • Under 22
  • 22 to 23
  • 23 to 28
  • 28 to 35
  • 35 to 41
  • 41 and over
  • No data
Median Air Quality Index (US EPA), 2025, index. Walla Walla 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

Median of the daily Air Quality Index (AQI) values of a US county over the days of the year with an AQI, from the EPA AirData annual summaries.

More on how it is measured
  • The daily county AQI is the highest AQI among the monitors and pollutants reported that day (ozone, PM2.5, PM10, carbon monoxide and nitrogen dioxide).
  • Lower is cleaner: 0 to 50 is good, 51 to 100 moderate and above 100 unhealthy for sensitive groups.

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: median 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: median daily AQI (Median Air Quality Index (US EPA), Walla Walla County, 1986 to 2025) [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: median daily AQI, Median Air Quality Index (US EPA), Walla Walla County, 1986 to 2025. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/en/median-air-quality-index/walla-walla-county-washington. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: median daily AQI. Median Air Quality Index (US EPA), Walla Walla County, 1986 to 2025. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/en/median-air-quality-index/walla-walla-county-washington.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: median daily AQI, Median Air Quality Index (US EPA), Walla Walla County, 1986 to 2025 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/en/median-air-quality-index/walla-walla-county-washington (Accessed: 12 October 2026).

BibTeX
@misc{environmental_median_air_quality_index_2025,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: median daily AQI: Median Air Quality Index (US EPA), Walla Walla County, 1986 to 2025}},
  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/median-air-quality-index/walla-walla-county-washington. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: median 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: median daily AQI: Median Air Quality Index (US EPA), Walla Walla County, 1986 to 2025
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/median-air-quality-index/walla-walla-county-washington
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/en/median-air-quality-index/walla-walla-county-washington.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: median 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 median Air Quality Index (US EPA) in Walla Walla County?

Median Air Quality Index (US EPA) in Walla Walla County was 28 in 2025, according to the U.S. Environmental Protection Agency. That is up 4 from 2024. That is the 15th highest of 31 counties in 2025.

Where does this figure come from?

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

What was the highest median Air Quality Index (US EPA) in Walla Walla County?

41 in 1986, the highest value since 1986 in this series.

Related statistics for Walla Walla County

All statistics for Walla Walla County | Walla Walla County in figures