Winona County, MN: EPA's radon zone, explained

EPA's own radon map rates Winona County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Rank it against the rest of the country and Winona County lands in the 90th percentile for radon potential.

Where Winona County sits nationally

Winona County, Minnesota is home to about 49,973 people across 626.191 square miles. That works out to roughly 80 people per square mile. By population, Winona County is the 313th largest of every county sharing its EPA zone — the 71st percentile by population within that zone. Geologically, Winona County is grouped into EPA Region 5 alongside 523 other counties that share its rock and soil setting.

What this actually means for a house in Winona County

Where the national indoor average runs about 1.3 pCi/L, Winona County's Zone 1 rating puts its predicted county average above EPA's 4 pCi/L action level itself. EPA's guidance doesn't change because of a Zone 1 label: test the house. What changes is the reason to not put it off in Winona County specifically.

If Winona County tests above the action level

For a Winona County homeowner, the order is simple: test first, since a kit costs a small fraction of what mitigation would. Only if the result clears 4 pCi/L does a system — typically $800–$2,500, about $1,200 for a common install — become worth pricing out.

Find Minnesota's state radon program

For Winona County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Winona County's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. Code RADONZONE-10OFF takes 10% off at checkout.

Where Winona County's figures come from

Winona County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.