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Air quality in South Dakota

EPA monitors report from 11 of South Dakota’s 66 counties. That is the honest limit of this page: the other 55 are not measured, not clean. In 2025 the most affected monitored county was Brown County, with 6 days above the moderate category.

11
Counties with monitors
55
Counties without
27
Days above moderate, 2025
Summed across monitored counties
10.2%
Adults with asthma
Population-weighted county estimate

County by county

Monitored South Dakota counties

GoodModerateUnhealthy for sensitive groupsUnhealthyVery unhealthyHazardous
County90th %ile AQIAbove moderateMax AQI2025 days by category
Brown County566115
Brookings County665154
Codington County584154
Minnehaha County584125
Union County644167
Clay County532117
Hughes County451112
Pennington County621107
Custer County58087
Jackson County55085
Meade County46071

EPA Air Quality System annual summaries by county, 2025. The 90th percentile AQI describes a day worse than nine out of ten, which is a steadier measure than the annual maximum a single wildfire can set.

Not measured

55 counties without a monitor

No EPA monitor reported from these counties, so there is no air quality record to publish. Their radon zone is known, and radon is measured in the building rather than the air outside it.

Other states

Air quality elsewhere