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Radon Levels in Sauk County, Wisconsin

EPA puts Sauk County in Zone 2, its middle radon zone, and high results are common there: 41.1% of the 241 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

    41.1%

    5.4 pts above WI

    Sauk
    41.1%
    Wisconsin
    35.7%

    241 tests, 2023

  • Median result

    3.3pCi/L

    Below action level

    Sauk
    3.3 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2023

  • Tests reported

    241

    24th of 69 by tests

    Sauk
    241
    Dane
    2,887

    Reported to CDC before any fix, 2023

  • EPA radon zone

    Zone 2

    Moderate potential

    1. 1
    2. Zone 2
    3. 3

    1 highest, 3 lowest

    EPA predicts 2 to 4 pCi/L indoors

  • Rank in Wisconsin

    28 of 69

    Middle half

    Sauk
    41.1%
    Langlade
    65.8%

    By share, of 69 with 30+ tests

Read a result for Sauk County

Starts at Sauk County's median, 3.3 pCi/L

3.3pCi/L

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

EPA’s reading of 3.3 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. Sauk County's median reported result, 2023.

Interpret this readingWhat a fix costs

The data

Sauk County, At a glance

Sauk County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Sauk County is a county: EPA's forecast for it as a whole is an average indoor of 2 to 4 pCi/L (75 to 150 Bq/m³). It describes no single address, and homes above EPA's are found in every zone, this one included.

USGS geologic potential: Moderate across 100% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Sauk County, 2023

Share of reported tests at or above 4 pCi/L, by year, Sauk County
Share of reported tests at or above 4 pCi/L, by year, Sauk County
YearShare of reported tests at or above 4 pCi/L
201442.6%
201547.7%
201640.6%
201737.1%
201933.8%
202031.2%
202135.3%
202249.3%
202341.1%

2023: 41.1%. Across these years the share ran from 31.2% to 49.3%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 241 tests reported to CDC for Sauk 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

Sauk County, Compared

Sauk County radon figures, compared

Calculated by Radon411

In Sauk County, about 4 in 10 reported tests in 2023 (99 of 241) were at or above EPA's action level. Against the national pool of 33.4%, the gap is 7.7 points higher. Across 72 Wisconsin counties pooled together, 35.7% of tests reached that level, so Sauk County runs 5.4 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 61.0% (Iowa County). By share, Sauk County is 28th of 69 Wisconsin counties with 30 or more tests for the same period.

Year by year, 2014 opened at 42.6% and 2023 closed at 41.1% (about level), with 2022 the high at 49.3%. Half the tests came in under 3.3 pCi/L and half over it; the single highest reached 36.7 pCi/L. Below the action level, 82 tests (34.0%) came in under 2 pCi/L, against 41.4% statewide, and 60 tests (24.9%) fell between 2 and 4, against 23.0% statewide.

Zone 2 on EPA's map (predicted average between 2 and 4 pCi/L) and a 41.1% share point the same way here. USGS geology rates 100% of the county's land moderate radon potential. CDC also counts 7 tests taken after mitigation in Sauk County for the same period: tests in homes where a fix was already in.

The busiest year on file was 2023, with 241 tests reported; the quietest, 2021, had 136.

Share of reported tests at or above 4 pCi/L by year, Sauk County against Wisconsin2014 to 2023, years with 30 or more tests: Sauk County 42.6% to 41.1%, the state's pooled share 35.7% in 2023.
Sauk CountyWisconsin, pooled
Share of reported tests at or above 4 pCi/L by year, Sauk County against Wisconsin: data table
YearTestsSauk County, at or above 4 pCi/LWisconsin, pooled
201418342.6%51.1%
201514947.7%51.6%
201619240.6%45.2%
201714337.1%44.8%
201916033.8%42.9%
202017031.2%27.0%
202113635.3%39.9%
202214449.3%42.9%
202324141.1%35.7%
Sauk County against Wisconsin, the United States and nearby counties, 2023
AreaTestsAt or above 4 pCi/LMedianDifference from Sauk County
Sauk County24141.1%3.3 pCi/LThis county
Wisconsin, pooled72 counties, pooled20,87935.7%Not pooled−5.4 points
United States, pooled642 counties, pooled128,74033.4%Not pooled−7.7 points
Langlade Countyhighest in the state22565.8%6.0 pCi/L+24.7 points
Bayfield Countylowest in the state355.7%1.5 pCi/L−35.4 points
Iowa County, WIborders it14661.0%4.8 pCi/L+19.9 points
Vernon County, WIborders it16247.5%3.8 pCi/L+6.4 points
Dane County, WIborders it2,88734.9%2.5 pCi/L−6.2 points
Richland County, WIborders it4833.3%2.9 pCi/L−7.8 points
Columbia County, WIborders it16328.8%2.0 pCi/L−12.3 points
Adams County, WIborders it4820.8%1.7 pCi/L−20.3 points
Juneau County, WIborders it5010.0%1.1 pCi/L−31.1 points
Where Sauk County's reported results fell, 2023, beside Wisconsin and the United States
ResultSauk County testsSauk County shareWisconsin shareU.S. shareAgainst Wisconsin
Under 2 pCi/L8234.0%41.4%41.4%−7.4 points
2 to 4 pCi/L6024.9%23.0%25.2%+1.9 points
4 pCi/L and above9941.1%35.7%33.4%+5.4 points
Sauk 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
Sawyer County23 of 694742.6%3.2 pCi/L
Kenosha County24 of 6941542.4%3.4 pCi/L
Winnebago County25 of 6951242.4%3.1 pCi/L
Door County26 of 6915642.3%3.0 pCi/L
Trempealeau County27 of 6911242.0%3.3 pCi/L
Sauk County28 of 6924141.1%3.3 pCi/L
Oneida County29 of 6913540.7%2.7 pCi/L
Outagamie County30 of 6933740.7%3.1 pCi/L
Green Lake County31 of 697940.5%3.4 pCi/L
Forest County32 of 694540.0%2.9 pCi/L
Jackson County33 of 699338.7%3.2 pCi/L
Sauk County radon tests by year, against Wisconsin's pooled share
YearTestsAt or above 4 pCi/LMedianHighestWisconsin, pooledChange from the row before
202324141.1%3.3 pCi/L36.7 pCi/L35.7%−8.2 points
202214449.3%3.8 pCi/L56.9 pCi/L42.9%+14.0 points
202113635.3%2.6 pCi/L66.4 pCi/L39.9%+4.1 points
202017031.2%2.5 pCi/L42.3 pCi/L27.0%−2.6 points
201916033.8%2.8 pCi/L40.2 pCi/L42.9%−3.3 points
201714337.1%3.2 pCi/L28.8 pCi/L44.8%−3.5 points
201619240.6%3.2 pCi/L66.7 pCi/L45.2%−7.1 points
201514947.7%3.7 pCi/L70.6 pCi/L51.6%+5.1 points
201418342.6%3.5 pCi/L33.6 pCi/L51.1%First on file

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

Sauk County, Geology

The ground under Sauk County

Predicted

Most of the ground under Sauk County is one class on USGS's geologic map: 99.9% of its land is moderate radon potential, with 0.1% high. The map puts 90.0% of Sauk County in the area it calls Driftless Area and 10.0% in Green Bay Lobe. USGS gives both a radon index of 10, in the moderate band (9 to 11).

USGS's geologic areas under Sauk County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Driftless AreaCambrian sandstone.Moderate1090.0%
Green Bay LobeGlacial deposits derived from carbonate and igneous rocks.Moderate1010.0%

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

Sauk County beside the ground around it

Wisconsin as a whole has more high-potential ground than Sauk County: 34.8% of its land, against 0.1% here. Of the 7 counties that border it, 5 have more high-potential ground, Iowa County the most at 94.7%.

Share of land by USGS radon potential: Sauk County, the 7 counties bordering it and Wisconsin
AreaEPA zoneLow potentialModerate potentialHigh potential
Sauk CountyZone 2None99.9%0.1%
Richland CountyZone 1None31.7%68.3%
Columbia CountyZone 2None64.1%35.9%
Iowa CountyZone 1None5.3%94.7%
Adams CountyZone 2None100%None
Juneau CountyZone 2None100%None
Dane CountyZone 1None28.0%72.0%
Vernon CountyZone 1None16.9%83.1%
Wisconsin72 counties, pooled by land areaVaries1.4%63.5%34.8%

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

Local help

Sauk County, Local resources

Radon testing and mitigation in Sauk 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

Sauk County, Questions

Questions about radon in Sauk County

Are radon levels high in Sauk County?

In 2023, 41.1% of the radon tests reported to CDC for Sauk County, Wisconsin were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.3 pCi/L. Of 69 Wisconsin counties with 30 or more tests for the same period, 27 reported a higher share; pooled, the state comes to 35.7%.

Which counties border Sauk County?

Sauk County borders 7 counties: Richland County, Columbia County, Iowa County, Adams County, Juneau County, Dane County and Vernon County.

Products

Sauk County, Products

Testing a home in Sauk County

In Sauk County, 41.1% of 241 tests reported to CDC in 2023 reached 4 pCi/L, against 35.7% pooled across Wisconsin. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Sauk County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Sauk County homes, compared

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Sauk County, Bordering counties

Counties bordering Sauk County

Calculated by Radon411

Sauk County, Cities and towns

Cities and towns in Sauk County

The Census Bureau estimates 66,652 residents in Sauk County for July 1, 2025, 856 more than in 2020 (+1.3%). That works out to 80 people per square mile of land. No town dominates: Baraboo, the largest, has 13,224 residents, 19.8% of the total. CDC's 241 reported tests for 2023 work out to 3.6 per 1,000 residents (2025 estimate), close to Wisconsin's 3.5.

From Baraboo to Lime Ridge, CDC publishes no figure by town: each reads Sauk County's.

The 12 largest cities and towns in Sauk County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Baraboo13,224+5.5%19.8%
Reedsburg10,641+5.7%16.0%
Prairie du Sac4,316−2.4%6.5%
Lake Delton3,451−1.6%5.2%
Sauk City3,439−2.1%5.2%
Wisconsin Dellsextends beyond Sauk County3,149+4.5%Counted whole
West Baraboo1,572−3.6%2.4%
Spring Green1,567+0.4%2.4%
Plain717−3.5%1.1%
North Freedom572−5.1%0.9%
Merrimac523+1.0%0.8%
Cazenoviaextends beyond Sauk County350−3.3%Counted whole
  • Rock Springs
  • La Valle
  • Loganville
  • Ironton
  • Lime Ridge

17 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. “(part)” marks a place that extends into another county. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025). A place that extends beyond Sauk County is counted whole, so it has no share.

Sauk County, Homes

Homes in Sauk County

Of Sauk County's 31,091 homes, 69% are detached houses, against 66% across Wisconsin; 13% are in buildings of five or more homes. Half of its homes were built before 1982, close to Wisconsin's 1975: 29% date from before 1960 and 25% from 2000 or later. 73% of occupied homes are lived in by their owner (Wisconsin: 68%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Sauk County, Wisconsin, 2019 to 2023
HomesSauk CountyWisconsin
Housing units31,0912,750,750
Detached houses69%66%
In buildings of 5 or more13%17%
Mobile homes7%3%
Built before 196029%34%
Built since 200025%20%
Middle year built19821975
Owner-occupied73%68%

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