Data / Share of days with good air quality (US EPA AQI) / Napa County

Share of days with good air quality (US EPA AQI) in Napa County

Share of days with good air quality (US EPA AQI) in Napa County was 77.1% in 2021, according to EPA. That is up 6.1 pts from 2020.

202177.1%
Change on 2020+6.1 pts
Series high98.92005
Series low25.72008

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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Share of days with good air quality (US EPA AQI) in Napa County, 1980 to 2021

20406080100198019861992199820042010201620211980: 75.1 %1981: 89.3 %1982: 87.1 %1983: 90.6 %1984: 85.2 %1985: 88.8 %1986: 86.6 %1987: 86 %1988: 83.1 %1989: 84.4 %1990: 87.7 %1991: 85.8 %1992: 92 %1993: 92.1 %1994: 95.1 %1995: 94 %1996: 94.3 %1997: 97.5 %1998: 94.5 %1999: 93.2 %2000: 97.5 %2001: 95.9 %2002: 96.7 %2003: 95.9 %2004: 97 %2005: 98.9 %2006: 95.6 %2007: 34 %2008: 25.7 %2009: 57.8 %2010: 58.9 %2011: 52.6 %2012: 61.2 %2013: 41.1 %2014: 30.4 %2015: 43.3 %2016: 59.8 %2017: 37.5 %2018: 57.7 %2019: 81.3 %2020: 71 %2021: 77.1 %2040608010019801994200820211980: 75.1 %1981: 89.3 %1982: 87.1 %1983: 90.6 %1984: 85.2 %1985: 88.8 %1986: 86.6 %1987: 86 %1988: 83.1 %1989: 84.4 %1990: 87.7 %1991: 85.8 %1992: 92 %1993: 92.1 %1994: 95.1 %1995: 94 %1996: 94.3 %1997: 97.5 %1998: 94.5 %1999: 93.2 %2000: 97.5 %2001: 95.9 %2002: 96.7 %2003: 95.9 %2004: 97 %2005: 98.9 %2006: 95.6 %2007: 34 %2008: 25.7 %2009: 57.8 %2010: 58.9 %2011: 52.6 %2012: 61.2 %2013: 41.1 %2014: 30.4 %2015: 43.3 %2016: 59.8 %2017: 37.5 %2018: 57.7 %2019: 81.3 %2020: 71 %2021: 77.1 %
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12, published 2026-07-13.
All 42 values
Period%
202177.1
202071
201981.3
201857.7
201737.5
201659.8
201543.3
201430.4
201341.1
201261.2
201152.6
201058.9
200957.8
200825.7
200734
200695.6
200598.9
200497
200395.9
200296.7
200195.9
200097.5
199993.2
199894.5
199797.5
199694.3
199594
199495.1
199392.1
199292
199185.8
199087.7
198984.4
198883.1
198786
198686.6
198588.8
198485.2
198390.6
198287.1
198189.3
198075.1

Napa County compared with nearby places

Alameda County: 42.5 %Amador County: 84.1 %Butte County: 43.8 %Calaveras County: 60.4 %Colusa County: 30.4 %Contra Costa County: 53.4 %Del Norte County: 80.2 %El Dorado County: 67.7 %Fresno County: 17 %Glenn County: 66.8 %Humboldt County: 91.2 %Imperial County: 23 %Inyo County: 27.4 %Kern County: 9.6 %Kings County: 23 %Lake County: 97.8 %Los Angeles County: 2.5 %Madera County: 36.4 %Marin County: 73.2 %Mariposa County: 52.9 %Mendocino County: 57.5 %Merced County: 42.5 %Mono County: 71.4 %Monterey County: 71.5 %Napa County: 77.1 %Nevada County: 50.1 %Orange County: 29.9 %Placer County: 35.6 %Plumas County: 26.6 %Riverside County: 5.2 %Sacramento County: 40 %San Benito County: 80.8 %San Bernardino County: 4.7 %San Diego County: 14.2 %San Francisco County: 69.9 %San Joaquin County: 38.4 %San Luis Obispo County: 42.2 %San Mateo County: 79.5 %Santa Barbara County: 65.8 %Santa Clara County: 40.3 %Santa Cruz County: 81.6 %Shasta County: 60.8 %Siskiyou County: 65.1 %Solano County: 58.9 %Sonoma County: 77.5 %Stanislaus County: 23 %Sutter County: 28 %Tehama County: 56.7 %Trinity County: 61.3 %Tulare County: 13.4 %Tuolumne County: 81.9 %Ventura County: 43 %Yolo County: 66.3 %
  • Under 23
  • 23 to 39
  • 39 to 53
  • 53 to 66
  • 66 to 77
  • 77 and over
  • No data
Share of days with good air quality (US EPA AQI), 2021, %. 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

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.

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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 (Share of days with good air quality (US EPA AQI), 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: good days as a share of days with an AQI, calculated with stored counts, Share of days with good air quality (US EPA AQI), 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/good-air-quality-days-share/napa-county-california. 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. Share of days with good air quality (US EPA AQI), 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/good-air-quality-days-share/napa-county-california.

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, Share of days with good air quality (US EPA AQI), Napa County, 1980 to 2021 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/en/good-air-quality-days-share/napa-county-california (Accessed: 12 October 2026).

BibTeX
@misc{environmental_share_of_days_with_2021,
  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: Share of days with good air quality (US EPA AQI), 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/good-air-quality-days-share/napa-county-california. 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: Share of days with good air quality (US EPA AQI), 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/good-air-quality-days-share/napa-county-california
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/en/good-air-quality-days-share/napa-county-california.
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

What is the share of days with good air quality (US EPA AQI) in Napa County?

Share of days with good air quality (US EPA AQI) in Napa County was 77.1% in 2021, according to EPA. That is up 6.1 pts from 2020.

Where does this figure come from?

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 by Invokely on 2026-10-12.

What was the highest share of days with good air quality (US EPA AQI) in Napa County?

98.9% in 2005, the highest value since 1980 in this series.

Related statistics for Napa County

All statistics for Napa County | Napa County in figures