Data / Share of days unhealthy for sensitive groups or worse (US EPA AQI) / Cascade County

Share of days unhealthy for sensitive groups or worse (US EPA AQI) in Cascade County

Share of days unhealthy for sensitive groups or worse (US EPA AQI) in Cascade County was 0% in 2024, according to EPA. That is down 1.7 pts from 2023.

20240%
Change on 2023-1.7 pts
Series high4.91980
Series low01982

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 unhealthy for sensitive groups or worse (US EPA AQI) in Cascade County, 1980 to 2024

01234519801987199420012008201520241980: 4.9 %1981: 0.6 %1982: 0 %1983: 0.8 %1984: 0.6 %1985: 0 %1986: 0.3 %1987: 1.2 %1988: 0.6 %1989: 0 %1990: 0 %1991: 0.6 %1992: 0 %1993: 0 %1994: 0 %1995: 0 %1996: 0 %1997: 0 %1998: 0 %1999: 0 %2000: 0.6 %2001: 0 %2002: 0 %2003: 0.8 %2004: 0 %2005: 0 %2006: 0 %2007: 0.8 %2008: 0 %2009: 0 %2010: 0 %2011: 0 %2012: 0.8 %2013: 0 %2014: 0.6 %2015: 2.6 %2016: 0 %2017: 0.3 %2018: 1.7 %2019: 0.3 %2020: 0.8 %2021: 3 %2022: 0.6 %2023: 1.7 %2024: 0 %024619801995201020241980: 4.9 %1981: 0.6 %1982: 0 %1983: 0.8 %1984: 0.6 %1985: 0 %1986: 0.3 %1987: 1.2 %1988: 0.6 %1989: 0 %1990: 0 %1991: 0.6 %1992: 0 %1993: 0 %1994: 0 %1995: 0 %1996: 0 %1997: 0 %1998: 0 %1999: 0 %2000: 0.6 %2001: 0 %2002: 0 %2003: 0.8 %2004: 0 %2005: 0 %2006: 0 %2007: 0.8 %2008: 0 %2009: 0 %2010: 0 %2011: 0 %2012: 0.8 %2013: 0 %2014: 0.6 %2015: 2.6 %2016: 0 %2017: 0.3 %2018: 1.7 %2019: 0.3 %2020: 0.8 %2021: 3 %2022: 0.6 %2023: 1.7 %2024: 0 %
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12, published 2026-07-13.
All 45 values
Period%
20240
20231.7
20220.6
20213
20200.8
20190.3
20181.7
20170.3
20160
20152.6
20140.6
20130
20120.8
20110
20100
20090
20080
20070.8
20060
20050
20040
20030.8
20020
20010
20000.6
19990
19980
19970
19960
19950
19940
19930
19920
19910.6
19900
19890
19880.6
19871.2
19860.3
19850
19840.6
19830.8
19820
19810.6
19804.9

Cascade County compared with nearby places

Beaverhead County: 0.6 %Cascade County: 0 %Custer County: 0.6 %Dawson County: 0.8 %Fergus County: 1.1 %Flathead County: 0 %Gallatin County: 0 %Glacier County: 0 %Hill County: 0.6 %Lake County: 0 %Lewis and Clark County: 1.6 %Lincoln County: 0.5 %Missoula County: 1.1 %Phillips County: 0.6 %Powell County: 1.8 %Ravalli County: 4.4 %Richland County: 1.4 %Roosevelt County: 1 %Rosebud County: 0 %Sanders County: 0 %Sheridan County: 1.7 %Silver Bow County: 1.4 %Teton County: 0.3 %Yellowstone County: 0.3 %
  • Under 0.5
  • 0.5 to 0.8
  • 0.8 to 1.4
  • 1.4 and over
  • No data
Share of days unhealthy for sensitive groups or worse (US EPA AQI), 2024, %. Cascade 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 above 100 (unhealthy for sensitive groups, unhealthy, very unhealthy or hazardous) 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; the counts are stored with each value.

Use the share rather than the number of days to compare counties, since the days with an AQI differ. 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: days with an AQI above 100 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: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts (Share of days unhealthy for sensitive groups or worse (US EPA AQI), Cascade County, 1980 to 2024) [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: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts, Share of days unhealthy for sensitive groups or worse (US EPA AQI), Cascade County, 1980 to 2024. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/en/unhealthy-air-quality-days-share/cascade-county-montana. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts. Share of days unhealthy for sensitive groups or worse (US EPA AQI), Cascade County, 1980 to 2024. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/en/unhealthy-air-quality-days-share/cascade-county-montana.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts, Share of days unhealthy for sensitive groups or worse (US EPA AQI), Cascade County, 1980 to 2024 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/en/unhealthy-air-quality-days-share/cascade-county-montana (Accessed: 12 October 2026).

BibTeX
@misc{environmental_share_of_days_unhealthy_2024,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts: Share of days unhealthy for sensitive groups or worse (US EPA AQI), Cascade County, 1980 to 2024}},
  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/unhealthy-air-quality-days-share/cascade-county-montana. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: days with an AQI above 100 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: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts: Share of days unhealthy for sensitive groups or worse (US EPA AQI), Cascade County, 1980 to 2024
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/unhealthy-air-quality-days-share/cascade-county-montana
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/en/unhealthy-air-quality-days-share/cascade-county-montana.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: days with an AQI above 100 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 unhealthy for sensitive groups or worse (US EPA AQI) in Cascade County?

Share of days unhealthy for sensitive groups or worse (US EPA AQI) in Cascade County was 0% in 2024, according to EPA. That is down 1.7 pts from 2023.

Where does this figure come from?

U.S. Environmental Protection Agency. EPA AirData annual AQI by county: days with an AQI above 100 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 unhealthy for sensitive groups or worse (US EPA AQI) in Cascade County?

4.9% in 1980, the highest value since 1980 in this series.

Related statistics for Cascade County

All statistics for Cascade County | Cascade County in figures