Highest daily Air Quality Index (US EPA) in Mason County
Highest daily Air Quality Index (US EPA) in Mason County was 87 in 2025, according to the U.S. Environmental Protection Agency. That is down 10 from 2024.
Highest daily Air Quality Index (US EPA) in Mason County, 1989 to 2025
All 37 values
| Period | index |
|---|---|
| 2025 | 87 |
| 2024 | 97 |
| 2023 | 143 |
| 2022 | 161 |
| 2021 | 115 |
| 2020 | 159 |
| 2019 | 64 |
| 2018 | 133 |
| 2017 | 108 |
| 2016 | 129 |
| 2015 | 105 |
| 2014 | 115 |
| 2013 | 112 |
| 2012 | 156 |
| 2011 | 172 |
| 2010 | 126 |
| 2009 | 133 |
| 2008 | 143 |
| 2007 | 177 |
| 2006 | 197 |
| 2005 | 187 |
| 2004 | 136 |
| 2003 | 187 |
| 2002 | 201 |
| 2001 | 187 |
| 2000 | 212 |
| 1999 | 215 |
| 1998 | 182 |
| 1997 | 195 |
| 1996 | 240 |
| 1995 | 216 |
| 1994 | 182 |
| 1993 | 200 |
| 1992 | 64 |
| 1991 | 222 |
| 1990 | 112 |
| 1989 | 79 |
Mason County compared with nearby places
- Under 110
- 110 to 140
- 140 to 150
- 150 to 160
- 160 and over
- No data
Rankings
Definition
Highest daily Air Quality Index (AQI) value recorded in a US county during the year, from the EPA AirData annual summaries. Values above 500 are beyond the AQI scale and are published as EPA computes them.
A single day decides the value, so one wildfire or dust event can set it. Dust from the dry Owens Lake bed puts Inyo and Mono counties in California in the thousands. 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: highest daily AQI. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.Citation styles
APA 7
U.S. Environmental Protection Agency. (2026). EPA AirData annual AQI by county: highest daily AQI (Highest daily Air Quality Index (US EPA), Mason County, 1989 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: highest daily AQI, Highest daily Air Quality Index (US EPA), Mason County, 1989 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/highest-daily-air-quality-index/mason-county-michigan. Accessed 12 Oct. 2026.
Chicago (author-date)
U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: highest daily AQI. Highest daily Air Quality Index (US EPA), Mason County, 1989 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/highest-daily-air-quality-index/mason-county-michigan.
Harvard
U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: highest daily AQI, Highest daily Air Quality Index (US EPA), Mason County, 1989 to 2025 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/en/highest-daily-air-quality-index/mason-county-michigan (Accessed: 12 October 2026).
BibTeX
@misc{environmental_highest_daily_air_quality_2025,
author = {{U.S. Environmental Protection Agency}},
title = {{EPA AirData annual AQI by county: highest daily AQI: Highest daily Air Quality Index (US EPA), Mason County, 1989 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/highest-daily-air-quality-index/mason-county-michigan. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest 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: highest daily AQI: Highest daily Air Quality Index (US EPA), Mason County, 1989 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/highest-daily-air-quality-index/mason-county-michigan
Y2 - 2026/10/12
N1 - Accessed via Invokely, https://invokely.ai/en/highest-daily-air-quality-index/mason-county-michigan.
N1 - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest daily AQI. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
ER -
Use this data in your AI agent
Invokely serves this figure to AI assistants through MCP and to code through a REST API, with the source and citation attached. Ask your assistant:
What is the latest highest daily Air Quality Index (US EPA) in Mason County? Cite the source.
get_value {"indicator":"aqi_max","place":"us-county-26105"}
GET https://invokely.ai/api/v1/value?indicator=aqi_max&place=us-county-26105Questions
What is the highest daily Air Quality Index (US EPA) in Mason County?
Highest daily Air Quality Index (US EPA) in Mason County was 87 in 2025, according to the U.S. Environmental Protection Agency. That is down 10 from 2024.
Where does this figure come from?
U.S. Environmental Protection Agency. EPA AirData annual AQI by county: highest daily AQI. Retrieved by Invokely on 2026-10-12.
What was the highest highest daily Air Quality Index (US EPA) in Mason County?
240 in 1996, the highest value since 1989 in this series.