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Radon Levels in Weston County, Wyoming

EPA puts Weston County in Zone 2, its middle radon zone, and high results are common there: 65.6% of the 32 radon tests reported to CDC (2008 to 2017, laboratory totals) 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

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  • Share at 4+ pCi/L

    65.6%

    21.3 pts above WY

    Weston
    65.6%
    Wyoming
    44.3%

    32 tests, 2008 to 2017

  • Median result

    6.3pCi/L

    Action level reached

    Weston
    6.3 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    32

    22nd of 22 by tests

    Weston
    32
    Laramie
    1,834

    Reported to CDC before any fix, 2008 to 2017

  • 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 Wyoming

    3 of 22

    Top quarter

    Weston
    65.6%
    Sheridan
    69.5%

    By share, of 22 with 30+ tests

Read a result for Weston County

Starts at Weston County's median, 6.3 pCi/L

6.3pCi/L

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

EPA’s reading of 6.3 pCi/L

At or above 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 at or above 4 pCi/L. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. Weston County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Weston County, At a glance

Weston County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Weston 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 55% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Weston County, 2008 to 2017, laboratory

Reported results by concentration band, Weston County, 2008 to 2017, laboratory
Under 2 pCi/L: 22%2 to 4 pCi/L: 12%4 pCi/L and above: 66%

Of 32 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Weston County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L721.9%
2 to 4 pCi/L412.5%
4 pCi/L and above2165.6%
What these figures count

These are the 32 tests reported to CDC for Weston County over 2008 to 2017 (laboratory totals), 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: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).

How to read these figures

Weston County, Compared

Weston County radon figures, compared

Calculated by Radon411

More than half: 65.6% of the 32 radon tests reported to CDC for Weston County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 3rd of 22 Wyoming counties with 30 or more tests for the same period. That is 21.3 points above the 44.3% pooled from 23 Wyoming counties.

The median result, 6.3 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 39.6 pCi/L. The rest split 21.9% under 2 pCi/L and 12.5% from 2 to 4 (Wyoming: 25.5% and 30.2%). The reported tests do not follow EPA's Zone 2 label for Weston County (predicted average between 2 and 4 pCi/L): 65.6% of them reached 4 pCi/L, fewer than that label suggests.

1 of its 6 bordering counties with figures ran higher, led by Custer County, SD at 65.7%; Campbell County reported 43.9%. Statewide for the same period, Sheridan County reported the highest share (69.5%) and Uinta County the lowest (24.6%).

CDC's ten-year totals for Weston County went from 33 tests (2005 to 2014) to 32 (2008 to 2017), the share going from 66.7% to 65.6%.

Nationally, every county with a figure for the same period pools to 35.7%; Weston County sits 29.9 points above it.

Weston County against Wyoming, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Weston County
Weston County3265.6%6.3 pCi/LThis county
Wyoming, pooled23 counties, pooled7,63844.3%Not pooled−21.3 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−29.9 points
Sheridan Countyhighest in the state84669.5%5.8 pCi/L+3.9 points
Uinta Countylowest in the state19924.6%2.2 pCi/L−41.0 points
Custer County, SDborders it10865.7%6.2 pCi/L+0.1 points
Converse County, WYborders it13062.3%4.8 pCi/L−3.3 points
Crook County, WYborders it5158.8%5.1 pCi/L−6.8 points
Lawrence County, SDborders it16056.9%5.3 pCi/L−8.7 points
Pennington County, SDborders it1,02953.6%4.3 pCi/L−12.0 points
Campbell County, WYborders it27143.9%3.5 pCi/L−21.7 points
Niobrara County, WYborders it1225.0%3.5 pCi/L−40.6 points
Where Weston County's reported results fell, 2008 to 2017, laboratory, beside Wyoming and the United States
ResultWeston County testsWeston County shareWyoming shareU.S. shareAgainst Wyoming
Under 2 pCi/L721.9%25.5%39.6%−3.6 points
2 to 4 pCi/L412.5%30.2%24.7%−17.7 points
4 pCi/L and above2165.6%44.3%35.7%+21.3 points
Weston County ranked among the 22 Wyoming counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Sheridan County1 of 2284669.5%5.8 pCi/L
Lincoln County2 of 2214268.3%7.8 pCi/L
Weston County3 of 223265.6%6.3 pCi/L
Converse County4 of 2213062.3%4.8 pCi/L
Crook County5 of 225158.8%5.1 pCi/L
Hot Springs County6 of 225955.9%4.2 pCi/L
Natrona County7 of 221,05455.7%4.3 pCi/L
Fremont County8 of 2261855.7%4.7 pCi/L
Sublette County9 of 226050.0%4.0 pCi/L
Sweetwater County10 of 2240949.6%3.9 pCi/L
Teton County11 of 2227844.6%3.4 pCi/L
Weston County ten-year laboratory totals, against Wyoming's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestWyoming, pooledChange from the row before
2008 to 20173265.6%6.3 pCi/L39.6 pCi/L44.3%−8.5 points
2007 to 20162774.1%7.3 pCi/L39.6 pCi/L44.6%+0.8 points
2006 to 20153073.3%7.2 pCi/L39.6 pCi/L45.3%+6.6 points
2005 to 20143366.7%6.4 pCi/L39.6 pCi/L45.5%First on file

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

Weston County, Geology

The ground under Weston County

Predicted

USGS's geologic map splits Weston County: 54.9% of its land is moderate radon potential and 45.1% high. The map puts 43.7% of Weston County in the area it calls East Powder River Basin and 26.3% in Powder River Basin, with 2 smaller areas beside them. USGS gives the first a radon index of 11, in the moderate band (9 to 11), and the second 12, in the high band (12 to 17).

USGS's geologic areas under Weston County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
East Powder River BasinUpper Cretaceous marine sedimentary rocks.Moderate1143.7%
Powder River BasinCretaceous and Tertiary uranium-bearing marginal-marine and fluvial sandstones.High1226.3%
Black HillsLate Paleozoic sedimentary or Precambrian intrusive igneous rocks.High1218.8%
Black HillsLate Paleozoic sedimentary or Precambrian intrusive igneous rocks.Moderate1111.2%

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

Weston County beside the ground around it

Wyoming as a whole has more high-potential ground than Weston County: 72.4% of its land, against 45.1% here. Of the 7 counties that border it, 3 have more high-potential ground, Campbell County the most at 97.6%.

Share of land by USGS radon potential: Weston County, the 7 counties bordering it and Wyoming
AreaEPA zoneLow potentialModerate potentialHigh potential
Weston CountyZone 2None54.9%45.1%
Niobrara CountyZone 1None69.5%30.5%
Custer County, SDZone 2None88.4%11.6%
Converse CountyZone 1None12.5%87.5%
Lawrence County, SDZone 2None89.5%10.5%
Campbell CountyZone 1None2.4%97.6%
Crook CountyZone 1None54.7%45.4%
Pennington County, SDZone 2None96.0%4.0%
Wyoming23 counties, pooled by land areaVariesNone27.6%72.4%

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

Local help

Weston County, Local resources

Radon testing and mitigation in Weston County

What it means

Weston County, Questions

Questions about radon in Weston County

Are radon levels high in Weston County?

Over the 2008 to 2017 laboratory totals, 65.6% of the radon tests reported to CDC for Weston County, Wyoming were at or above 4 pCi/L, and the median reported pre-mitigation result was 6.3 pCi/L. Of 22 Wyoming counties with 30 or more tests for the same period, 2 reported a higher share; pooled, the state comes to 44.3%.

Which counties border Weston County?

Weston County borders 7 counties: Niobrara County, WY, Custer County, SD, Converse County, WY, Lawrence County, SD, Campbell County, WY, Crook County, WY and Pennington County, SD.

Products

Weston County, Products

Testing a home in Weston County

In Weston County, 65.6% of 32 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 44.3% pooled across Wyoming. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Weston County; a long-term test tells the year-round average.

Test kits and monitors3

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Best radon monitors for Weston County homes, compared

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Weston County, Bordering counties

Counties bordering Weston County

Calculated by Radon411

Weston County, Cities and towns

Cities and towns in Weston County

Weston County's population has barely moved since 2020: 6,840 residents on July 1, 2025 against 6,820 then, by the Census Bureau's estimates. Spread over its land, that is 2.9 people to the square mile. Its largest town, Newcastle, has 3,349 residents, 49.0% of the total. Together its 2 incorporated places hold 62.1% of those residents; the other 37.9% live outside any of them. Reported testing is thin here: 32 tests over 2008 to 2017, or 4.7 for every 1,000 residents (2025 estimate), where Wyoming as a whole comes to 13.0.

From Newcastle to Upton, CDC publishes no figure by town: each reads Weston County's.

The cities and towns in Weston County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Newcastle3,349−0.4%49.0%
Upton897+0.2%13.1%

2 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).

Weston County, Homes

Homes in Weston County

Of Weston County's 3,417 homes, 74% are detached houses, against 68% across Wyoming; 17% are mobile homes. Half of its homes were built before 1976, close to Wyoming's 1980: 39% date from before 1960 and 23% from 2000 or later. Owners live in 89% of the occupied homes (Wyoming: 72%), so for most households a test and a fix are their own to order.

Homes in Weston County, Wyoming, 2019 to 2023
HomesWeston CountyWyoming
Housing units3,417275,131
Detached houses74%68%
In buildings of 5 or more5%9%
Mobile homes17%12%
Built before 196039%24%
Built since 200023%24%
Middle year built19761980
Owner-occupied89%72%

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