What EPA's radon map says about Okanogan County

EPA's own radon map rates Okanogan County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Nationally that's the 89th percentile for radon potential — Okanogan County outranks 89% of every county EPA has rated.

Where Okanogan County sits nationally

About 44,942 people live in Okanogan County, Washington, spread over 5,266.193 square miles. Population density there runs about 9 people per square mile. Among counties sharing Okanogan County's EPA zone, it outranks 67% of them by population. Geologically, Okanogan County is grouped into EPA Region 10 alongside 141 other counties that share its rock and soil setting.

What this actually means for a house in Okanogan County

Okanogan County's predicted average sits above EPA's own action level of 4 pCi/L — the concentration at which EPA recommends fixing a home — versus a national average around 1.3 pCi/L indoors and 0.4 pCi/L outdoors. A Zone 1 rating means testing is worth doing sooner rather than later, but it is still county-wide average, not a reading for any single house — some homes in Okanogan County will test well under the action level, and EPA's guidance is to test regardless of zone.

Next steps for a home in Okanogan County

Mitigation cost doesn't depend on Okanogan County's zone — it depends on the house's foundation. A typical system runs $800–$2,500 (about $1,200 typical), and testing first is what tells you whether that's needed at all.

Find Washington's state radon program

Okanogan County's test kit answers today; a Airthings radon monitor keeps answering for Okanogan County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. Code RADONZONE-10OFF takes 10% off at checkout.

More on how this number was built

The methodology guide shows exactly which EPA and Census sources feed Okanogan County's numbers. Whatever zone Okanogan County carries, the zone explainer covers what it does and doesn't tell you about any one house.