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Radon Levels in Vernon County, Wisconsin

EPA puts Vernon County in Zone 1, its highest radon zone, and high results are common there: 47.5% of the 162 radon tests reported to CDC (2023) came back at or above 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.

Data checked By Radon411Methodology

How to test this homeFind a certified tester

  • Share at 4+ pCi/L

    47.5%

    11.8 pts above WI

    Vernon
    47.5%
    Wisconsin
    35.7%

    162 tests, 2023

  • Median result

    3.8pCi/L

    Below action level

    Vernon
    3.8 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2023

  • Tests reported

    162

    34th of 69 by tests

    Vernon
    162
    Dane
    2,887

    Reported to CDC before any fix, 2023

  • EPA radon zone

    Zone 1

    Highest potential

    1. Zone 1
    2. 2
    3. 3

    1 highest, 3 lowest

    EPA predicts over 4 pCi/L indoors

  • Rank in Wisconsin

    15 of 69

    Top quarter

    Vernon
    47.5%
    Langlade
    65.8%

    By share, of 69 with 30+ tests

Read a result for Vernon County

Starts at Vernon County's median, 3.8 pCi/L

3.8pCi/L

EPA’s own thresholds; the figures are the area’s, never this home’s.

EPA’s reading of 3.8 pCi/L

Between 2 and 4 pCi/L

  1. Under 20 to 1.9 pCi/L
  2. 2 to 4consider a fix
  3. 4 and aboveEPA says fix it

This result is between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Vernon County's median reported result, 2023.

Interpret this readingWhat a fix costs

The data

Vernon County, At a glance

Vernon County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Vernon County in and predicts an average indoor of greater than 4 pCi/L (greater than 150 Bq/m³) across the county. That is one forecast for the whole county, not a reading of any address in it; homes above EPA's turn up in all three zones.

USGS geologic potential: High across 83% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Vernon County, 2023

Share of reported tests at or above 4 pCi/L, by year, Vernon County
Share of reported tests at or above 4 pCi/L, by year, Vernon County
YearShare of reported tests at or above 4 pCi/L
201459.8%
201562.7%
201649.0%
201769.8%
201964.9%
202050.6%
202163.4%
202220.1%
202347.5%

2023: 47.5%. Across these years the share ran from 20.1% to 69.8%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 162 tests reported to CDC for Vernon County over 2023, many from homes being sold or already suspected of a problem: they describe the county's reported tests, not this house.

Measured: CDC tracking data. Figure above: 2023. Measured data period: 2005 to 2023 (every CDC figure on file).

How to read these figures

Vernon County, Compared

Vernon County radon figures, compared

Calculated by Radon411

In Vernon County, about 5 in 10 reported tests in 2023 (77 of 162) were at or above EPA's action level. Against the national pool of 33.4%, the gap is 14.1 points higher. Across 72 Wisconsin counties pooled together, 35.7% of tests reached that level, so Vernon County runs 11.8 points above its state.

Of 7 neighbours with a figure, 2 reported a larger share at or above 4 pCi/L and 5 a smaller one; the spread is 10.0% (Juneau County) to 53.9% (Crawford County). By share, Vernon County is 15th of 69 Wisconsin counties with 30 or more tests for the same period.

Year by year, 2014 opened at 59.8% and 2023 closed at 47.5% (down 12.3 points), with 2017 the high at 69.8%. Half the tests came in under 3.8 pCi/L and half over it; the single highest reached 157.7 pCi/L. Below the action level, 45 tests (27.8%) came in under 2 pCi/L, against 41.4% statewide, and 40 tests (24.7%) fell between 2 and 4, against 23.0% statewide.

Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 47.5% share point the same way here. USGS geology rates 83% of the county's land high radon potential.

The busiest year on file was 2022, with 298 tests reported; the quietest, 2014, had 82.

Share of reported tests at or above 4 pCi/L by year, Vernon County against Wisconsin2014 to 2023, years with 30 or more tests: Vernon County 59.8% to 47.5%, the state's pooled share 35.7% in 2023.
Vernon CountyWisconsin, pooled
Share of reported tests at or above 4 pCi/L by year, Vernon County against Wisconsin: data table
YearTestsVernon County, at or above 4 pCi/LWisconsin, pooled
20148259.8%51.1%
201512662.7%51.6%
201614349.0%45.2%
20179669.8%44.8%
201918564.9%42.9%
20208950.6%27.0%
202119463.4%39.9%
202229820.1%42.9%
202316247.5%35.7%
Vernon County against Wisconsin, the United States and nearby counties, 2023
AreaTestsAt or above 4 pCi/LMedianDifference from Vernon County
Vernon County16247.5%3.8 pCi/LThis county
Wisconsin, pooled72 counties, pooled20,87935.7%Not pooled−11.8 points
United States, pooled642 counties, pooled128,74033.4%Not pooled−14.1 points
Langlade Countyhighest in the state22565.8%6.0 pCi/L+18.3 points
Bayfield Countylowest in the state355.7%1.5 pCi/L−41.8 points
Crawford County, WIborders it21753.9%4.4 pCi/L+6.4 points
Houston County, MNborders it11347.8%3.5 pCi/L+0.3 points
Sauk County, WIborders it24141.1%3.3 pCi/L−6.4 points
Richland County, WIborders it4833.3%2.9 pCi/L−14.2 points
La Crosse County, WIborders it77131.4%2.7 pCi/L−16.1 points
Monroe County, WIborders it21322.5%2.2 pCi/L−25.0 points
Juneau County, WIborders it5010.0%1.1 pCi/L−37.5 points
Where Vernon County's reported results fell, 2023, beside Wisconsin and the United States
ResultVernon County testsVernon County shareWisconsin shareU.S. shareAgainst Wisconsin
Under 2 pCi/L4527.8%41.4%41.4%−13.6 points
2 to 4 pCi/L4024.7%23.0%25.2%+1.7 points
4 pCi/L and above7747.5%35.7%33.4%+11.8 points
Vernon County ranked among the 69 Wisconsin counties with 30 or more tests, by share at or above 4 pCi/L, 2023
CountyRankTestsAt or above 4 pCi/LMedian
Marathon County10 of 6934951.9%4.3 pCi/L
Calumet County11 of 6912251.6%4.4 pCi/L
Rock County12 of 6945149.9%3.9 pCi/L
Grant County13 of 6932348.3%3.5 pCi/L
Washington County14 of 6939947.9%3.8 pCi/L
Vernon County15 of 6916247.5%3.8 pCi/L
Ozaukee County16 of 6944545.8%3.6 pCi/L
Washburn County17 of 694944.9%3.1 pCi/L
Kewaunee County18 of 695644.6%3.7 pCi/L
Marinette County19 of 696144.3%2.6 pCi/L
Jefferson County20 of 6929644.3%3.5 pCi/L
Vernon County radon tests by year, against Wisconsin's pooled share
YearTestsAt or above 4 pCi/LMedianHighestWisconsin, pooledChange from the row before
202316247.5%3.8 pCi/L157.7 pCi/L35.7%+27.4 points
202229820.1%1.0 pCi/L101.0 pCi/L42.9%−43.3 points
202119463.4%5.2 pCi/L173.5 pCi/L39.9%+12.8 points
20208950.6%4.3 pCi/L29.8 pCi/L27.0%−14.3 points
201918564.9%5.3 pCi/L35.5 pCi/L42.9%−4.9 points
20179669.8%5.8 pCi/L53.1 pCi/L44.8%+20.8 points
201614349.0%3.9 pCi/L23.2 pCi/L45.2%−13.7 points
201512662.7%5.8 pCi/L72.3 pCi/L51.6%+2.9 points
20148259.8%5.2 pCi/L25.2 pCi/L51.1%First on file

Pooled shares: Radon411's sum of CDC's county counts for one period.

Vernon County, Geology

The ground under Vernon County

Predicted

Most of the ground under Vernon County is one class on USGS's geologic map: 83.1% of its land is high radon potential, with 16.9% moderate. The map puts 82.9% of Vernon County in the area it calls Driftless Area and 16.9% in Driftless Area. USGS gives the first a radon index of 12, in the high band (12 to 17), and the second 10, in the moderate band (9 to 11).

USGS's geologic areas under Vernon County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Driftless AreaCambrian sandstone and Ordovician limestone and dolostone.High1282.9%
Driftless AreaCambrian sandstone.Moderate1016.9%

Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.

Vernon County beside the ground around it

Vernon County has more high-potential ground than Wisconsin as a whole: 83.1% of its land against 34.8%. Of the 8 counties that border it, 3 have more high-potential ground, Crawford County the most at 100%.

Share of land by USGS radon potential: Vernon County, the 8 counties bordering it and Wisconsin
AreaEPA zoneLow potentialModerate potentialHigh potential
Vernon CountyZone 1None16.9%83.1%
Monroe CountyZone 2None91.2%8.8%
Crawford CountyZone 1NoneNone100%
Richland CountyZone 1None31.7%68.3%
La Crosse CountyZone 2None66.4%33.6%
Allamakee County, IAZone 1NoneNone100%
Houston County, MNZone 1NoneNone100%
Juneau CountyZone 2None100%None
Sauk CountyZone 2None99.9%0.1%
Wisconsin72 counties, pooled by land areaVaries1.4%63.5%34.8%

The map rates the ground, not the air in any home.

Local help

Vernon County, Local resources

Radon testing and mitigation in Vernon County

What Wisconsin's program says
Phone
1-888-569-7236
Email
DHSRadon@dhs.wisconsin.gov
Licensing of radon professionals
The State of Wisconsin does not require contractors performing radon measurement or mitigation work to be state licensed or nationally certified.

What it means

Vernon County, Questions

Questions about radon in Vernon County

Are radon levels high in Vernon County?

In 2023, 47.5% of the radon tests reported to CDC for Vernon County, Wisconsin were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.8 pCi/L. Of 69 Wisconsin counties with 30 or more tests for the same period, 14 reported a higher share; pooled, the state comes to 35.7%.

Which counties border Vernon County?

Vernon County borders 8 counties: Monroe County, WI, Crawford County, WI, Richland County, WI, La Crosse County, WI, Allamakee County, IA, Houston County, MN, Juneau County, WI and Sauk County, WI.

Products

Vernon County, Products

Testing a home in Vernon County

In Vernon County, 47.5% of 162 tests reported to CDC in 2023 reached 4 pCi/L, against 35.7% pooled across Wisconsin. In Zone 1 the year-round level in Vernon County is the one to know: a long-term test (more than 90 days) or a monitor, with a short-term kit for a first answer.

Test kits and monitors3

See every kit and monitor

Vernon County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Vernon County

Explore

Vernon County, Bordering counties

Counties bordering Vernon County

Calculated by Radon411

Vernon County, Cities and towns

Cities and towns in Vernon County

The Census Bureau estimates 31,443 residents in Vernon County for July 1, 2025, 748 more than in 2020 (+2.4%). That works out to 40 people per square mile of land. No town dominates: Viroqua, the largest, has 4,435 residents, 14.1% of the total. CDC's 162 reported tests for 2023 work out to 5.2 per 1,000 residents (2025 estimate), close to Wisconsin's 3.5.

From Viroqua to Genoa, CDC publishes no figure by town: each reads Vernon County's.

The cities and towns in Vernon County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Viroqua4,435−2.2%14.1%
Westby2,435+2.3%7.7%
Hillsboro1,401−0.4%4.5%
Stoddard911+8.8%2.9%
Coon Valley760+0.5%2.4%
Violaextends beyond Vernon County728+9.1%Counted whole
La Farge701−2.4%2.2%
Ontarioextends beyond Vernon County528−0.8%Counted whole
Readstown370−1.6%1.2%
De Sotoextends beyond Vernon County323+5.6%Counted whole
Chaseburg240−0.8%0.8%
Genoa228−1.7%0.7%

12 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025). A place that extends beyond Vernon County is counted whole, so it has no share.

Vernon County, Homes

Homes in Vernon County

Vernon County is a place of houses on their own lots: 82% of its 13,939 homes are detached single-family houses, against 66% across Wisconsin. Half of its homes were built before 1974, close to Wisconsin's 1975: 39% date from before 1960 and 21% from 2000 or later. Owners live in 81% of the occupied homes (Wisconsin: 68%), so for most households a test and a fix are their own to order.

Homes in Vernon County, Wisconsin, 2019 to 2023
HomesVernon CountyWisconsin
Housing units13,9392,750,750
Detached houses82%66%
In buildings of 5 or more5%17%
Mobile homes9%3%
Built before 196039%34%
Built since 200021%20%
Middle year built19741975
Owner-occupied81%68%

Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.