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

Median Air Quality Index (US EPA) in Sonoma County

Median Air Quality Index (US EPA) in Sonoma County was 9 in 2025, according to the U.S. Environmental Protection Agency. That is down 10 from 2024.

2025, index9
Change on 2024-10
Series high422014
Series low92025

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 Sonoma County, 1980 to 2025

0102030405019801987199420012008201520251980: 38 index1981: 38 index1982: 35 index1983: 30 index1984: 35 index1985: 37 index1986: 33 index1987: 37 index1988: 37 index1989: 35 index1990: 35 index1991: 37 index1992: 37 index1993: 37 index1994: 37 index1995: 37 index1996: 37 index1997: 35 index1998: 37 index1999: 38 index2000: 37 index2001: 37 index2002: 37 index2003: 37 index2004: 33 index2005: 32 index2006: 34 index2007: 35 index2008: 37 index2009: 33 index2010: 36 index2011: 40 index2012: 41 index2013: 41 index2014: 42 index2015: 37 index2016: 34 index2017: 41 index2018: 39 index2019: 36 index2020: 36 index2021: 37 index2022: 36 index2023: 33 index2024: 19 index2025: 9 index0102030405019801996201220251980: 38 index1981: 38 index1982: 35 index1983: 30 index1984: 35 index1985: 37 index1986: 33 index1987: 37 index1988: 37 index1989: 35 index1990: 35 index1991: 37 index1992: 37 index1993: 37 index1994: 37 index1995: 37 index1996: 37 index1997: 35 index1998: 37 index1999: 38 index2000: 37 index2001: 37 index2002: 37 index2003: 37 index2004: 33 index2005: 32 index2006: 34 index2007: 35 index2008: 37 index2009: 33 index2010: 36 index2011: 40 index2012: 41 index2013: 41 index2014: 42 index2015: 37 index2016: 34 index2017: 41 index2018: 39 index2019: 36 index2020: 36 index2021: 37 index2022: 36 index2023: 33 index2024: 19 index2025: 9 index
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12, published 2026-07-13.
All 46 values
Periodindex
20259
202419
202333
202236
202137
202036
201936
201839
201741
201634
201537
201442
201341
201241
201140
201036
200933
200837
200735
200634
200532
200433
200337
200237
200137
200037
199938
199837
199735
199637
199537
199437
199337
199237
199137
199035
198935
198837
198737
198633
198537
198435
198330
198235
198138
198038

Sonoma County compared with nearby places

Amador County: 38 indexButte County: 46 indexCalaveras County: 40 indexColusa County: 40 indexDel Norte County: 32 indexEl Dorado County: 40 indexFresno County: 61 indexGlenn County: 40 indexHumboldt County: 38 indexImperial County: 64 indexInyo County: 55 indexKern County: 70 indexKings County: 57 indexLake County: 31 indexLos Angeles County: 74 indexMadera County: 50 indexMarin County: 21 indexMariposa County: 44 indexMendocino County: 38 indexMerced County: 50 indexMono County: 21 indexMonterey County: 38 indexNevada County: 42 indexOrange County: 53 indexPlacer County: 52 indexPlumas County: 45 indexRiverside County: 80 indexSacramento County: 49 indexSan Benito County: 39 indexSan Bernardino County: 77 indexSan Diego County: 67 indexSan Joaquin County: 46 indexSan Luis Obispo County: 50 indexSanta Barbara County: 52 indexSanta Cruz County: 35 indexShasta County: 44 indexSiskiyou County: 37 indexSolano County: 33 indexSonoma County: 9 indexStanislaus County: 51 indexSutter County: 47 indexTehama County: 38 indexTrinity County: 31 indexTulare County: 64 indexTuolumne County: 39 indexVentura County: 50 indexYolo County: 47 index
  • Under 36
  • 36 to 39
  • 39 to 45
  • 45 to 50
  • 50 to 58
  • 58 and over
  • No data
Median Air Quality Index (US EPA), 2025, index. Sonoma 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), Sonoma County, 1980 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), Sonoma County, 1980 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/sonoma-county-california. 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), Sonoma County, 1980 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/sonoma-county-california.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: median daily AQI, Median Air Quality Index (US EPA), Sonoma County, 1980 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/sonoma-county-california (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), Sonoma County, 1980 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/sonoma-county-california. 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), Sonoma County, 1980 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/sonoma-county-california
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/en/median-air-quality-index/sonoma-county-california.
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 Sonoma County?

Median Air Quality Index (US EPA) in Sonoma County was 9 in 2025, according to the U.S. Environmental Protection Agency. That is down 10 from 2024.

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 Sonoma County?

42 in 2014, the highest value since 1980 in this series.

Related statistics for Sonoma County

All statistics for Sonoma County | Sonoma County in figures