Highest daily Air Quality Index (US EPA)
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.
Key facts
- Mono County had the highest highest daily Air Quality Index (US EPA) of 1000 counties in 2019, at 4,227, and Alexandria city the lowest, at 16. Source: the U.S. Environmental Protection Agency.
- Published for 1,498 places, with figures from 1980 to 2025.
Rankings
- US counties
- Counties in Texas
- Counties in North Carolina
- Counties in Virginia
- Counties in California
- Counties in Ohio
- Counties in Kentucky
- Counties in Indiana
- Counties in Michigan
- Counties in Wisconsin
- Counties in Oklahoma
- Counties in Pennsylvania
US counties by highest daily Air Quality Index (US EPA), 2019
Places with data
Provinces and counties
- Los Angeles County
- Cook County
- Harris County
- Maricopa County
- San Diego County
- Orange County
- Miami-Dade County
- Dallas County
- Kings County
- Riverside County
- Nassau County
- Frederick County
- Erie County
- Kent County
- Imperial County
- Horry County
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:
Which places have the highest highest daily Air Quality Index (US EPA)? Use official data and cite it.
rank_places {"indicator":"aqi_max","level":"province","within":"United States"}
GET https://invokely.ai/api/v1/rank?indicator=aqi_max&level=province&within=United%20States