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

Median Air Quality Index (US EPA) in Napa County

Median Air Quality Index (US EPA) in Napa County was 41 in 2021, according to the U.S. Environmental Protection Agency. That is up 2 from 2020.

2021, index41
Change on 2020+2
Series high552007
Series low311983

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 Napa County, 1980 to 2021

303540455055198019861992199820042010201620211980: 38 index1981: 34 index1982: 38 index1983: 31 index1984: 34 index1985: 35 index1986: 37 index1987: 38 index1988: 37 index1989: 34 index1990: 33 index1991: 35 index1992: 32 index1993: 35 index1994: 31 index1995: 31 index1996: 32 index1997: 31 index1998: 31 index1999: 32 index2000: 31 index2001: 31 index2002: 32 index2003: 31 index2004: 31 index2005: 31 index2006: 34 index2007: 55 index2008: 55 index2009: 46 index2010: 46 index2011: 49 index2012: 44 index2013: 53 index2014: 55 index2015: 53 index2016: 44 index2017: 53 index2018: 46 index2019: 37 index2020: 39 index2021: 41 index3040506019801994200820211980: 38 index1981: 34 index1982: 38 index1983: 31 index1984: 34 index1985: 35 index1986: 37 index1987: 38 index1988: 37 index1989: 34 index1990: 33 index1991: 35 index1992: 32 index1993: 35 index1994: 31 index1995: 31 index1996: 32 index1997: 31 index1998: 31 index1999: 32 index2000: 31 index2001: 31 index2002: 32 index2003: 31 index2004: 31 index2005: 31 index2006: 34 index2007: 55 index2008: 55 index2009: 46 index2010: 46 index2011: 49 index2012: 44 index2013: 53 index2014: 55 index2015: 53 index2016: 44 index2017: 53 index2018: 46 index2019: 37 index2020: 39 index2021: 41 index
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12, published 2026-07-13.
All 42 values
Periodindex
202141
202039
201937
201846
201753
201644
201553
201455
201353
201244
201149
201046
200946
200855
200755
200634
200531
200431
200331
200232
200131
200031
199932
199831
199731
199632
199531
199431
199335
199232
199135
199033
198934
198837
198738
198637
198535
198434
198331
198238
198134
198038

Napa County compared with nearby places

Alameda County: 53 indexAmador County: 37 indexButte County: 53 indexCalaveras County: 46 indexColusa County: 55 indexContra Costa County: 47 indexDel Norte County: 31 indexEl Dorado County: 43 indexFresno County: 68 indexGlenn County: 42 indexHumboldt County: 29 indexImperial County: 60 indexInyo County: 61 indexKern County: 84 indexKings County: 64 indexLake County: 33 indexLos Angeles County: 79 indexMadera County: 58 indexMarin County: 38 indexMariposa County: 49 indexMendocino County: 46 indexMerced County: 54 indexMono County: 27 indexMonterey County: 41 indexNapa County: 41 indexNevada County: 50 indexOrange County: 55 indexPlacer County: 58 indexPlumas County: 67 indexRiverside County: 89 indexSacramento County: 55 indexSan Benito County: 41 indexSan Bernardino County: 87 indexSan Diego County: 67 indexSan Francisco County: 39 indexSan Joaquin County: 55 indexSan Luis Obispo County: 53 indexSan Mateo County: 36 indexSanta Barbara County: 44 indexSanta Clara County: 53 indexSanta Cruz County: 37 indexShasta County: 46 indexSiskiyou County: 43 indexSolano County: 44 indexSonoma County: 37 indexStanislaus County: 61 indexSutter County: 59 indexTehama County: 47 indexTrinity County: 38 indexTulare County: 81 indexTuolumne County: 41 indexVentura County: 53 indexYolo County: 42 index
  • Under 38
  • 38 to 43
  • 43 to 49
  • 49 to 55
  • 55 to 62
  • 62 and over
  • No data
Median Air Quality Index (US EPA), 2021, index. Napa 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), Napa County, 1980 to 2021) [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), Napa County, 1980 to 2021. 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/napa-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), Napa County, 1980 to 2021. 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/napa-county-california.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: median daily AQI, Median Air Quality Index (US EPA), Napa County, 1980 to 2021 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/en/median-air-quality-index/napa-county-california (Accessed: 12 October 2026).

BibTeX
@misc{environmental_median_air_quality_index_2021,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: median daily AQI: Median Air Quality Index (US EPA), Napa County, 1980 to 2021}},
  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/napa-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), Napa County, 1980 to 2021
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/napa-county-california
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/en/median-air-quality-index/napa-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 Napa County?

Median Air Quality Index (US EPA) in Napa County was 41 in 2021, according to the U.S. Environmental Protection Agency. That is up 2 from 2020.

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 Napa County?

55 in 2007, the highest value since 1980 in this series.

Related statistics for Napa County

All statistics for Napa County | Napa County in figures