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

Median Air Quality Index (US EPA) in Whatcom County

Median Air Quality Index (US EPA) in Whatcom County was 31 in 2025, according to the U.S. Environmental Protection Agency. That is down 2 from 2024. That is the 13th highest of 31 counties in 2025.

2025, index31
Change on 2024-2
Rank13th of 31Counties in Washington ranked
Series high441986
Series low241988

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 Whatcom County, 1986 to 2025

20253035404519861992199820042010201620251986: 44 index1987: 43 index1988: 24 index1989: 27 index1990: 30 index1991: 31 index1992: 34 index1993: 31 index1994: 31 index1995: 31 index1996: 31 index1997: 31 index1998: 30 index1999: 33 index2000: 31 index2001: 33 index2002: 36 index2003: 36 index2004: 31 index2005: 33 index2006: 34 index2007: 32 index2008: 31 index2009: 33 index2010: 32 index2011: 30 index2012: 26 index2013: 33 index2014: 38 index2015: 34 index2016: 28 index2017: 31 index2018: 29 index2019: 29 index2020: 24 index2021: 28 index2022: 32 index2023: 31 index2024: 33 index2025: 31 index20253035404519862000201420251986: 44 index1987: 43 index1988: 24 index1989: 27 index1990: 30 index1991: 31 index1992: 34 index1993: 31 index1994: 31 index1995: 31 index1996: 31 index1997: 31 index1998: 30 index1999: 33 index2000: 31 index2001: 33 index2002: 36 index2003: 36 index2004: 31 index2005: 33 index2006: 34 index2007: 32 index2008: 31 index2009: 33 index2010: 32 index2011: 30 index2012: 26 index2013: 33 index2014: 38 index2015: 34 index2016: 28 index2017: 31 index2018: 29 index2019: 29 index2020: 24 index2021: 28 index2022: 32 index2023: 31 index2024: 33 index2025: 31 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
202531
202433
202331
202232
202128
202024
201929
201829
201731
201628
201534
201438
201333
201226
201130
201032
200933
200831
200732
200634
200533
200431
200336
200236
200133
200031
199933
199830
199731
199631
199531
199431
199331
199234
199131
199030
198927
198824
198743
198644

Whatcom 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. Whatcom 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), Whatcom 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), Whatcom 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/whatcom-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), Whatcom 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/whatcom-county-washington.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: median daily AQI, Median Air Quality Index (US EPA), Whatcom 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/whatcom-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), Whatcom 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/whatcom-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), Whatcom 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/whatcom-county-washington
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/en/median-air-quality-index/whatcom-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 Whatcom County?

Median Air Quality Index (US EPA) in Whatcom County was 31 in 2025, according to the U.S. Environmental Protection Agency. That is down 2 from 2024. That is the 13th 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 Whatcom County?

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

Related statistics for Whatcom County

All statistics for Whatcom County | Whatcom County in figures