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

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

Share of days with good air quality (US EPA AQI) in Weld County was 44.7% in 2025, according to EPA. That is up 4 pts from 2024. That is the 30th highest of 30 counties in 2025.

202544.7%
Change on 2024+4 pts
Rank30th of 30Counties in Colorado ranked
Series high86.61993
Series low37.82018

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Share of days with good air quality (US EPA AQI) in Weld County, 1980 to 2025

3040506070809019801987199420012008201520251980: 71.9 %1981: 68.4 %1982: 70.9 %1983: 69.5 %1984: 70.5 %1985: 74.5 %1986: 70.1 %1987: 67.4 %1988: 68.3 %1989: 75.3 %1990: 79.5 %1991: 77.3 %1992: 83.8 %1993: 86.6 %1994: 80.5 %1995: 82.2 %1996: 78.4 %1997: 83 %1998: 75.6 %1999: 75.1 %2000: 72.7 %2001: 68.8 %2002: 59 %2003: 56.4 %2004: 61.5 %2005: 62.2 %2006: 50.7 %2007: 56.7 %2008: 64.2 %2009: 72.6 %2010: 58.1 %2011: 56.4 %2012: 53.6 %2013: 59.2 %2014: 65.5 %2015: 61.4 %2016: 54.9 %2017: 47.4 %2018: 37.8 %2019: 41.6 %2020: 45.4 %2021: 42.7 %2022: 46.6 %2023: 40 %2024: 40.7 %2025: 44.7 %
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12, published 2026-07-13.
All 46 values
Period%
202544.7
202440.7
202340
202246.6
202142.7
202045.4
201941.6
201837.8
201747.4
201654.9
201561.4
201465.5
201359.2
201253.6
201156.4
201058.1
200972.6
200864.2
200756.7
200650.7
200562.2
200461.5
200356.4
200259
200168.8
200072.7
199975.1
199875.6
199783
199678.4
199582.2
199480.5
199386.6
199283.8
199177.3
199079.5
198975.3
198868.3
198767.4
198670.1
198574.5
198470.5
198369.5
198270.9
198168.4
198071.9

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.

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

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), Weld County, 1980 to 2025 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/en/good-air-quality-days-share/weld-county-colorado (Accessed: 12 October 2026).

BibTeX
@misc{environmental_share_of_days_with_2025,
  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), Weld 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/good-air-quality-days-share/weld-county-colorado. 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), Weld 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/good-air-quality-days-share/weld-county-colorado
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/en/good-air-quality-days-share/weld-county-colorado.
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 Weld County?

Share of days with good air quality (US EPA AQI) in Weld County was 44.7% in 2025, according to EPA. That is up 4 pts from 2024. That is the 30th highest of 30 counties in 2025.

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 Weld County?

86.6% in 1993, the highest value since 1980 in this series.

Related statistics for Weld County

All statistics for Weld County | Weld County in figures