Is Winnebago County, WI a radon risk area?

EPA's own radon map rates Winnebago County zone 2 - moderate potential, predicting a county-wide average indoor level between 2 and 4 pCi/L. That puts Winnebago County in the 62nd percentile nationally for radon potential — higher than 62% of the counties EPA has rated.

Winnebago County by the numbers

About 173,307 people live in Winnebago County, Wisconsin, spread over 434.697 square miles. Averaged across its land area, Winnebago County runs about 399 people per square mile. Rank 136 by population within its EPA zone puts Winnebago County at the 87th percentile among zone peers. EPA's geology-based Region 5 groups Winnebago County with 523 other counties nationally sharing its underlying rock and soil profile.

Why the zone isn't the answer by itself

Winnebago County's predicted average falls between EPA's 4 pCi/L action level and the national indoor average of about 1.3 pCi/L (outdoor air runs roughly 0.4 pCi/L). A county-wide moderate average, like Winnebago County's, can still hide a specific house well above or below it — testing is what actually answers the question.

Next steps for a home in Winnebago County

Nothing about Winnebago County's EPA zone changes the mitigation number: $800–$2,500 nationally (around $1,200 typical), set by the house's foundation rather than the county it sits in — and only relevant once a test actually clears 4 pCi/L.

Find Wisconsin's state radon program

Winnebago County's test kit answers today; a Airthings radon monitor keeps answering for Winnebago County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. Use code RADONZONE-10OFF at checkout for 10% off.

More on how this number was built

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.