Data / Median Air Quality Index (US EPA) / Del Norte County

Median Air Quality Index (US EPA) in Del Norte County

Median Air Quality Index (US EPA) in Del Norte County was 32 in 2025, according to the U.S. Environmental Protection Agency. That is unchanged from 2024.

2025, index32
Change on 20240
Series high422020
Series low122012

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 Del Norte County, 1987 to 2025

102030405019871993199920052011201720251987: 27 index1988: 28 index1989: 26 index1990: 30 index1991: 28 index1992: 31 index1993: 29 index1994: 31 index1995: 31 index1996: 18 index1997: 20 index1998: 16 index1999: 17 index2000: 18 index2001: 17 index2002: 20 index2003: 14 index2004: 15 index2005: 16 index2006: 16 index2007: 16 index2008: 17 index2009: 14 index2010: 14 index2011: 17 index2012: 12 index2013: 16 index2014: 16 index2015: 20 index2016: 26 index2017: 27 index2018: 33 index2019: 26 index2020: 42 index2021: 31 index2022: 29 index2023: 32 index2024: 32 index2025: 32 index102030405019872000201320251987: 27 index1988: 28 index1989: 26 index1990: 30 index1991: 28 index1992: 31 index1993: 29 index1994: 31 index1995: 31 index1996: 18 index1997: 20 index1998: 16 index1999: 17 index2000: 18 index2001: 17 index2002: 20 index2003: 14 index2004: 15 index2005: 16 index2006: 16 index2007: 16 index2008: 17 index2009: 14 index2010: 14 index2011: 17 index2012: 12 index2013: 16 index2014: 16 index2015: 20 index2016: 26 index2017: 27 index2018: 33 index2019: 26 index2020: 42 index2021: 31 index2022: 29 index2023: 32 index2024: 32 index2025: 32 index
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12, published 2026-07-13.
All 39 values
Periodindex
202532
202432
202332
202229
202131
202042
201926
201833
201727
201626
201520
201416
201316
201212
201117
201014
200914
200817
200716
200616
200516
200415
200314
200220
200117
200018
199917
199816
199720
199618
199531
199431
199329
199231
199128
199030
198926
198828
198727

Del Norte 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. Del Norte 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), Del Norte County, 1987 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), Del Norte County, 1987 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/del-norte-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), Del Norte County, 1987 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/del-norte-county-california.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: median daily AQI, Median Air Quality Index (US EPA), Del Norte County, 1987 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/del-norte-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), Del Norte County, 1987 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/del-norte-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), Del Norte County, 1987 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/del-norte-county-california
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/en/median-air-quality-index/del-norte-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 Del Norte County?

Median Air Quality Index (US EPA) in Del Norte County was 32 in 2025, according to the U.S. Environmental Protection Agency. That is unchanged 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 Del Norte County?

42 in 2020, the highest value since 1987 in this series.

Related statistics for Del Norte County

All statistics for Del Norte County | Del Norte County in figures