Indicator · us-ozone-days
Days when ozone set the AQI
The pollutant with the highest AQI that day.
- Unit
- % of days
- Places
- 916 counties in 2025
- Built from
- Yearly air quality summary by county
Map and compare every county on visualizedata.org →
Median county, 1980–2025
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Show the data as a table
Highest and lowest in 2025
| Adams County, IL | 100.0% of days |
|---|---|
| Aiken County, SC | 100.0% of days |
| Alexander County, NC | 100.0% of days |
| Amador County, CA | 100.0% of days |
| Anderson County, SC | 100.0% of days |
177 counties share this value; five are shown, alphabetically.
| Yakima County, WA | 0.0% of days |
|---|---|
| Wyoming County, PA | 0.0% of days |
| Wilson County, TX | 0.0% of days |
| Whitman County, WA | 0.0% of days |
| Whitley County, IN | 0.0% of days |
175 counties share this value; five are shown, alphabetically.
How it is computed
EPA days ozone was the main pollutant / days with an AQI, from the Yearly air quality summary by county dataset on this site. visualizedata.org computes the indicator for every place and year; the full table, the map and each place's history are on its page there. The underlying data, with its source and license, is on the dataset page, with the API and downloads.