Radon Levels by Minnesota County
Minnesota measures its radon problem better than almost any state: the Minnesota Department of Health publishes real test results county by county on its Public Health Data Access portal, plus an interactive county map. This guide explains what that data shows, what it hides, and how to use it before testing your own home.
The statewide picture first
Two MDH findings frame every county number. First, 2 in 5 Minnesota homes tested have radon levels that pose a significant health risk. Second, the average radon level in Minnesota runs more than three times higher than the U.S. average. MDH attributes both to geology, uranium decaying naturally in rocks and soil, and to a long heating season that pulls soil gas into homes people actually live in through the winter. No Minnesota county is exempt from that mechanism.
Verified county figures
Every figure below traces to the named primary source. Counties without an independently verified local figure are best represented by the statewide numbers above and by the MDH portal itself; this table does not estimate.
| County | What the data shows | Source |
|---|---|---|
| Olmsted (Rochester) | 48.6% of properties tested 2010 to 2020 at or above 4 pCi/L | MDH county test data |
| Winona | Roughly half of tested homes elevated, per county environmental health estimates | Winona County |
| St. Louis (Duluth) | About 29.5% of tested properties at or above 4 pCi/L; about 59% at or above 2 pCi/L | MDH county test data |
| Hennepin (Minneapolis, Bloomington) | EPA Zone 1, predicted average indoor level above 4 pCi/L | EPA Map of Radon Zones, Minnesota |
| Ramsey (St. Paul) | EPA Zone 1, predicted average indoor level above 4 pCi/L | EPA Map of Radon Zones, Minnesota |
| Stearns (St. Cloud) | EPA Zone 1, predicted average indoor level above 4 pCi/L | EPA Map of Radon Zones, Minnesota |
| Blue Earth (Mankato) | EPA Zone 1, predicted average indoor level above 4 pCi/L | EPA Map of Radon Zones, Minnesota |
| Clay (Moorhead) | EPA Zone 1, predicted average indoor level above 4 pCi/L | EPA Map of Radon Zones, Minnesota |
| Beltrami (Bemidji) | EPA Zone 2, predicted average between 2 and 4 pCi/L; MDH still advises testing | EPA Map of Radon Zones, Minnesota |
How to read county radon data honestly
Three cautions keep the numbers useful. Tested properties are not all properties: results come from homes whose owners chose to test, so the data skews toward transactions and aware homeowners. County averages hide house-to-house swings: two neighbors routinely differ by multiples, which is why MDH pushes individual testing over map reading. And zone ratings are predictions, not measurements: the EPA drew its Minnesota zone map from geology and available data to set priorities, not to clear individual homes in any county.
Why the counties differ: a 90-second geology tour
The southeast tests highest, sitting on karst: soluble limestone and dolomite, fractured and sinkhole-pocked, documented in the DNR karst mapping, which gives soil gas open lanes toward basements in places like Rochester and Winona. The west sits on the clay bed of Glacial Lake Agassiz, described by the DNR as a poorly drained silty and clayey plain. The northeast around Duluth runs on near-surface igneous bedrock with thin soils, and nearly everything else lies under the glacial till the Minnesota Geological Survey maps statewide. Different rocks, same uranium decay chain, per MDH.
From data to action
Whatever your county shows, the sequence is identical: test your home, and if the result is at or above 4 pCi/L, get a written quote from a licensed contractor, with costs covered in our Minnesota cost guide. Local context for the biggest markets is on our city pages, including Rochester, Duluth, St. Paul, and Bemidji.