Long-term kit
RL116 long-term radon test kit
- Lab fee extra
Method: Alpha track
In home: 90 days to 12 months
Locations and reports
Radon Levels in St. Croix County, Wisconsin
EPA puts St. Croix County in Zone 1, its highest radon zone, and 37.4% of its 348 reported radon tests (2023) were 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
Share at 4+ pCi/L
37.4%
1.7 pts above WI
- St. Croix
- 37.4%
- Wisconsin
- 35.7%
348 tests, 2023
Median result
3.0pCi/L
Below action level
- St. Croix
- 3.0 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2023
Tests reported
348
16th of 69 by tests
- St. Croix
- 348
- Dane
- 2,887
Reported to CDC before any fix, 2023
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
EPA predicts over 4 pCi/L indoors
Rank in Wisconsin
37 of 69
Middle half
- St. Croix
- 37.4%
- Langlade
- 65.8%
By share, of 69 with 30+ tests
Read a result for St. Croix County
Starts at St. Croix County's median, 3.0 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 3.0 pCi/L
Between 2 and 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 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. St. Croix County's median reported result, 2023.
The data
St. Croix County, At a glance
St. Croix County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of St. Croix County in
USGS geologic potential: High across 100% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for St. Croix County, 2023
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 52.6% |
| 2015 | 49.5% |
| 2016 | 45.5% |
| 2017 | 49.8% |
| 2019 | 52.6% |
| 2020 | 43.4% |
| 2021 | 43.9% |
| 2022 | 55.2% |
| 2023 | 37.4% |
2023: 37.4%. Across these years the share ran from 37.4% to 55.2%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 348 tests reported to CDC for St. Croix 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).
St. Croix County, Compared
St. Croix County radon figures, compared
Calculated by Radon411In St. Croix County, about 4 in 10 reported tests in 2023 (130 of 348) were at or above EPA's action level. Against the national pool of 33.4%, the gap is 4.0 points higher. Across 72 Wisconsin counties pooled together, 35.7% of tests reached that level, so St. Croix County runs 1.7 points above its state.
Of 5 neighbours with a figure, none reported a larger share at or above 4 pCi/L; the spread is 21.3% (Washington County, MN) to 37.4% (Dunn County). By share, St. Croix County is 37th of 69 Wisconsin counties with 30 or more tests for the same period.
Year by year, 2014 opened at 52.6% and 2023 closed at 37.4% (down 15.2 points), with 2022 the high at 55.2%. Half the tests came in under 3.0 pCi/L and half over it; the single highest reached 54.9 pCi/L. Below the action level, 125 tests (35.9%) came in under 2 pCi/L, against 41.4% statewide, and 93 tests (26.7%) fell between 2 and 4, against 23.0% statewide.
Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 37.4% share point the same way here. USGS geology rates 100% of the county's land high radon potential. CDC also counts 8 tests taken after mitigation in St. Croix County for the same period: tests in homes where a fix was already in.
The busiest year on file was 2015, with 521 tests reported; the quietest, 2021, had 173.
St. Croix CountyWisconsin, pooled
| Year | Tests | St. Croix County, at or above 4 pCi/L | Wisconsin, pooled |
|---|---|---|---|
| 2014 | 489 | 52.6% | 51.1% |
| 2015 | 521 | 49.5% | 51.6% |
| 2016 | 387 | 45.5% | 45.2% |
| 2017 | 311 | 49.8% | 44.8% |
| 2019 | 291 | 52.6% | 42.9% |
| 2020 | 198 | 43.4% | 27.0% |
| 2021 | 173 | 43.9% | 39.9% |
| 2022 | 212 | 55.2% | 42.9% |
| 2023 | 348 | 37.4% | 35.7% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
St. Croix County, Geology
The ground under St. Croix County
PredictedMost of the ground under St. Croix County is one class on USGS's geologic map: 99.7% of its land is high radon potential, with 0.3% moderate. 99.4% of it lies in the area the map calls Western Highlands, to which USGS gives a radon index of 12, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Western Highlands | Glacial deposits derived largely from Ordovician carbonate rocks. | High | 12 | 99.4% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
St. Croix County beside the ground around it
St. Croix County has more high-potential ground than Wisconsin as a whole: 99.7% of its land against 34.8%. Of the 5 counties that border it, 2 have more high-potential ground, Pierce County the most at 100%.
The map rates the ground, not the air in any home.
Local help
St. Croix County, Local resources
Radon testing and mitigation in St. Croix County
Listed radon businesses with an address in St. Croix County:
- Wisconsin's radon programWisconsin Department of Health ServicesWisconsin's radon program does not license radon professionals and offers free or discounted test kits, and answers questions about testing and mitigation in Wisconsin.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
We recommend starting with your regional Radon Information Center since many centers provide test kits for free or reduced cost, and often with laboratory fees covered.
- Compare kits
- Professionals in Wisconsin19 professionals are listed in Wisconsin.
Listed radon professionals by town: River Falls, Hudson, New Richmond, Roberts, Wilson
What Wisconsin's program says
- Phone
- 1-888-569-7236
- 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
St. Croix County, Questions
Questions about radon in St. Croix County
Are radon levels high in St. Croix County?
In 2023, 37.4% of the radon tests reported to CDC for St. Croix County, Wisconsin were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.0 pCi/L. Of 69 Wisconsin counties with 30 or more tests for the same period, 36 reported a higher share; pooled, the state comes to 35.7%.
Which counties border St. Croix County?
St. Croix County borders 5 counties: Washington County, MN, Pierce County, WI, Dunn County, WI, Polk County, WI and Barron County, WI.
Products
St. Croix County, Products
Testing a home in St. Croix County
In St. Croix County, 37.4% of 348 tests reported to CDC in 2023 reached 4 pCi/L, against 35.7% pooled across Wisconsin. In Zone 1 the year-round level in St. Croix 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
MonitorPYZYCKYH
RD17 plug-in radon detector with a rechargeable battery and color screen
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
Method: Semiconductor sensor
First reading: Within 6 hours
Short-term kit
PicoCan short-term charcoal canister radon test
- Lab fee included
Method: Charcoal
In home: 48 to 96 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
St. Croix County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like St. Croix County
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St. Croix County, Bordering counties
Counties bordering St. Croix County
Calculated by Radon411- Radon levels in Dunn County, WIEPA zone 2
37.4%at or above 4 pCi/L
Median 2.9 pCi/L · 171 tests · 0.0 points above St. Croix County
- Radon levels in Barron County, WIEPA zone 2
34.7%at or above 4 pCi/L
Median 2.5 pCi/L · 199 tests · 2.7 points below St. Croix County
- Radon levels in Polk County, WIEPA zone 2
33.6%at or above 4 pCi/L
Median 2.8 pCi/L · 122 tests · 3.8 points below St. Croix County
- Radon levels in Pierce County, WIEPA zone 1
30.9%at or above 4 pCi/L
Median 2.7 pCi/L · 136 tests · 6.5 points below St. Croix County
- Radon levels in Washington County, MNEPA zone 1
21.3%at or above 4 pCi/L
Median 1.9 pCi/L · 1,518 tests · 16.1 points below St. Croix County
St. Croix County, Cities and towns
Cities and towns in St. Croix County
The Census Bureau estimates 98,276 residents in St. Croix County for July 1, 2025, 4,401 more than in 2020 (+4.7%). That works out to 136 people per square mile of land. River Falls, the largest place on its list (17,916 residents in all), extends beyond St. Croix County, so no share of the total is worked out for it. CDC's 348 reported tests for 2023 work out to 3.5 per 1,000 residents (2025 estimate), close to Wisconsin's 3.5.
From River Falls to Wilson, CDC publishes no figure by town: each reads St. Croix County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| River Fallsextends beyond St. Croix County | 17,916 | +9.9% | Counted whole |
| Hudson | 15,019 | +1.3% | 15.3% |
| New Richmond | 10,988 | +8.2% | 11.2% |
| Baldwin | 4,347 | +1.2% | 4.4% |
| North Hudson | 3,803 | −0.3% | 3.9% |
| Somerset | 3,408 | +12.5% | 3.5% |
| Roberts | 2,493 | +29.2% | 2.5% |
| Hammond | 1,857 | −2.4% | 1.9% |
| Spring Valleyextends beyond St. Croix County | 1,443 | +2.9% | Counted whole |
| Woodville | 1,389 | −0.4% | 1.4% |
| Glenwood City | 1,254 | −3.5% | 1.3% |
| Star Prairie | 656 | −2.7% | 0.7% |
- Deer Park
- Wilson
14 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 St. Croix County is counted whole, so it has no share.
St. Croix County, Homes
Homes in St. Croix County
Of St. Croix County's 38,185 homes, 74% are detached houses, against 66% across Wisconsin; 9% are in buildings of five or more homes. Much of St. Croix County is recent building: 39% of its homes have gone up since 2000 and the middle year built is 1993, against 1975 for Wisconsin. Owners live in 79% of the occupied homes (Wisconsin: 68%), so for most households a test and a fix are their own to order.
| Homes | St. Croix County | Wisconsin |
|---|---|---|
| Housing units | 38,185 | 2,750,750 |
| Detached houses | 74% | 66% |
| In buildings of 5 or more | 9% | 17% |
| Mobile homes | 3% | 3% |
| Built before 1960 | 18% | 34% |
| Built since 2000 | 39% | 20% |
| Middle year built | 1993 | 1975 |
| Owner-occupied | 79% | 68% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.