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Air quality in Wisconsin

EPA monitors report from 29 of Wisconsin’s 72 counties. That is the honest limit of this page: the other 43 are not measured, not clean. In 2025 the most affected monitored county was Kenosha County, with 19 days above the moderate category.

29
Counties with monitors
43
Counties without
193
Days above moderate, 2025
Summed across monitored counties
10.8%
Adults with asthma
Population-weighted county estimate

County by county

Monitored Wisconsin counties

GoodModerateUnhealthy for sensitive groupsUnhealthyVery unhealthyHazardous
County90th %ile AQIAbove moderateMax AQI2025 days by category
Kenosha County7719167
Milwaukee County7416175
Ozaukee County6715167
Forest County6414182
Ashland County6213188
Brown County6611175
Eau Claire County6211174
Jackson County6310172
Waukesha County6910172
Marathon County619168
Monroe County629165
Outagamie County649172
Racine County778122
Dodge County637171
Sheboygan County777156
Dane County646170
Sauk County586167
Grant County633167
Walworth County673112
Columbia County581108
Door County641108
Jefferson County541105
Kewaunee County671105
Manitowoc County581115
Rock County611108
Vilas County491105
Fond du Lac County50080
La Crosse County49090
Taylor County46097

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

43 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