Indicator · us-unhealthy-days
Days with unhealthy air
AQI above 100, counties with a monitor reading at least 180 days.
- Unit
- days
- Places
- 916 counties in 2025
- Built from
- Yearly air quality summary by county
- Reading it
- Lower is better.
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
| San Bernardino County, CA | 110 days |
|---|---|
| Riverside County, CA | 109 days |
| Los Angeles County, CA | 98 days |
| Kern County, CA | 65 days |
| El Paso County, TX | 63 days |
| York County, SC | 0 days |
|---|---|
| Yolo County, CA | 0 days |
| Yellowstone County, MT | 0 days |
| Yavapai County, AZ | 0 days |
| Yalobusha County, MS | 0 days |
374 counties share this value; five are shown, alphabetically.
How it is computed
EPA days unhealthy for sensitive groups or worse, 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.