1. The Short Answer
The best time to test for radon is whenever you have not tested before. Do not wait for a specific season. Every month of delay is another month of potential exposure if your home has elevated levels.
That said, if you want to be strategic about testing, here is what to know: winter testing (November through February) captures the highest radon levels and gives you a worst-case picture of your exposure. Summer testing tends to produce lower readings. Both are valid, but understanding the seasonal patterns helps you interpret your results correctly.
Bottom Line
Test now. If your result is above 4 pCi/L, mitigate regardless of season. If your result is borderline (2 to 4 pCi/L) during summer, plan to retest during winter for a worst-case reading. If your winter result is below 2 pCi/L, you can feel confident.
2. Why Season Matters for Radon Testing
Radon levels in your home are not constant. They fluctuate with weather, barometric pressure, wind, soil moisture, and most significantly, the temperature difference between indoor and outdoor air.
The primary driver of seasonal radon variation is the stack effect. When warm air inside your home rises and escapes through the upper levels, it creates negative pressure at the lower levels. This pressure differential pulls soil gas (including radon) into your home through the foundation. The greater the temperature difference between inside and outside, the stronger this effect.
In Georgia, winter temperatures regularly drop into the 30s and 40s while homes are heated to 68-72°F. That 25-40 degree differential drives significant radon infiltration. In summer, the differential reverses: it is hotter outside than inside, which can actually reduce the stack effect in some homes. However, tightly sealed homes with central air may still pull soil gas through foundation cracks.
| Season | Typical Radon Levels | Key Factor |
|---|---|---|
| Winter (Nov-Feb) | Highest | Strong stack effect, closed house |
| Spring (Mar-May) | Moderate to high | Transitional, wet soil can trap radon |
| Summer (Jun-Sep) | Lowest | Reduced stack effect, some natural ventilation |
| Fall (Oct-Nov) | Moderate, rising | Stack effect increasing as temps drop |
3. Winter Testing in Georgia (November - February)
Winter is considered the ideal time for radon testing because it captures your highest exposure. When the heating system runs and windows stay shut, your home is essentially sealed up, and the stack effect is at its strongest. The radon level you measure in January is a reasonable representation of your worst-case scenario.
Advantages of Winter Testing
Georgia winters are mild compared to northern states, but the temperature differential is still significant enough to drive radon infiltration. Metro Atlanta averages around 42°F in January, creating a 25-30 degree differential with heated interiors.
4. Summer Testing in Georgia (June - September)
Summer radon levels in Georgia are typically the lowest of the year, but that does not mean they are always safe. A home that tests at 6 pCi/L in summer could easily reach 12 to 15 pCi/L in winter. Conversely, a summer reading of 1 pCi/L is reassuring that your home's radon situation is manageable.
Georgia Summer Caveat
Georgia's hot, humid summers mean most homes are tightly sealed with air conditioning running 24/7. While the thermal stack effect may be reduced, the airtight conditions can still concentrate radon. Homes with forced-air HVAC systems may pull soil gas through foundation penetrations where ductwork or refrigerant lines enter the slab. Do not assume summer automatically means low radon.
How to Interpret Summer Results
5. Spring and Fall: The Transition Seasons
Spring (March through May) and fall (October through November) are transition seasons for radon. Levels are generally moderate, falling between winter peaks and summer lows. These seasons have their own characteristics that affect testing.
Spring in Georgia
Spring brings heavy rainfall to Georgia, which is relevant to radon. Saturated soil can act as a cap, preventing radon from escaping into the atmosphere and directing it into the path of least resistance: your foundation. After heavy rain events, radon levels can temporarily spike. Spring also brings fluctuating temperatures, with some weeks feeling like winter and others like summer, creating variable radon conditions.
Fall in Georgia
Fall is when radon levels begin their climb toward the winter peak. As temperatures drop and homeowners switch from air conditioning to heating, the stack effect strengthens. October and November often show a noticeable increase over September levels. Fall testing gives you a preview of what winter will bring.
Both seasons are perfectly valid for testing. The key is knowing how to interpret results in the context of when you tested. A spring reading of 3.5 pCi/L suggests you are likely above 4 pCi/L in winter. A fall reading of 3.5 pCi/L is even more likely to be higher in the months ahead.
6. Testing During Real Estate Transactions
When buying or selling a home, you test when the transaction happens. You cannot wait for winter to close on a home you are buying in July. The inspection period dictates the testing timeline, not the season.
This is where professional testing matters most. A CRM provides hourly data that gives context beyond a single number. An experienced radon professional can interpret the data in light of seasonal factors and advise whether the result warrants mitigation or seasonal retesting. Learn more about the complete timeline in our guide on how long radon testing takes.
For sellers: if you are listing in spring or summer and your last test was in winter, provide the winter results to buyers. A winter test showing low radon is more convincing than a summer test. If you have not tested, consider getting ahead of it. Check your area with our radon risk lookup to gauge the likelihood. Read our full guide on radon and Georgia real estate.
Negotiation Tip
If a summer radon test comes back at 3-4 pCi/L during a home purchase, buyers can reasonably argue that winter levels would likely exceed 4 pCi/L and request mitigation as part of the deal. A professional radon tester can provide seasonal adjustment context to support this negotiation.
7. When to Retest Your Home
Testing once is a good start. But radon levels change over time as soil conditions shift, homes settle, and foundations develop new cracks. The EPA recommends retesting on a regular schedule:
For a complete retesting schedule, see our how often to test for radon guide. If you are wondering about cost, use our cost estimator to plan ahead.
