Summer Radon Levels in Georgia: Why Testing Still Matters in Warm Months

There is a widespread belief that radon levels drop significantly in summer and that testing can wait until the colder months. This idea comes from northern states where homeowners open windows and spend summer days with fresh air flowing through the house. In those climates, summer radon levels genuinely tend to be lower.

Georgia is different. Summer in Atlanta means temperatures regularly above 90 degrees, humidity that feels like a wall, and air conditioning running around the clock. Nobody is opening windows from June through September. Your home is sealed up just as tightly as it is in January, sometimes more so.

This means the conditions that allow radon to accumulate indoors, specifically a sealed building envelope with limited fresh air exchange, exist in Georgia during summer just as they do during winter. The mechanism is slightly different (AC vs. heating), but the practical effect on your indoor air is similar.

Radon is produced continuously by the natural decay of uranium in the soil and rock beneath your home. It does not take vacations. The soil beneath your foundation generates radon 365 days a year, regardless of the temperature outside.

Your air conditioning system has several effects on radon dynamics inside your home. Understanding these can help you make sense of why summer testing is still important.

The net effect is that Georgia homes during summer are operating under conditions that can sustain meaningful radon concentrations. You are spending more time indoors in that air, making summer exposure a real consideration.

Georgia summers are famously humid, and that humidity plays a role in radon dynamics. The soil around your foundation stays consistently moist during the summer months, thanks to a combination of high ambient humidity, afternoon thunderstorms, and morning dew.

Moist soil acts as a cap over the ground surface. When the top layer of soil is saturated, radon gas cannot escape into the open atmosphere as easily. Instead, it gets redirected laterally through the soil and can concentrate beneath your foundation slab. From there, it enters through the same pathways it always uses: cracks in the slab, gaps around pipes, sump pits, and construction joints.

Crawl space homes are particularly affected by summer humidity. Moisture buildup in an unsealed crawl space can increase the rate at which radon enters from the soil, and that contaminated air can be pulled into the living space above through gaps in the floor system, ductwork, and plumbing penetrations.

The radon in your home comes from uranium in the rock and soil beneath the surface. In the Atlanta metro area and throughout north Georgia, the underlying geology includes granite and gneiss formations that contain measurable amounts of uranium. This uranium decays through a chain of elements, eventually producing radon gas.

This process is entirely geological. It is not affected by the temperature outside, the season, or the weather. The same amount of uranium is decaying beneath your foundation in July as in January. The rate of radon production is constant year-round.

What changes seasonally is not how much radon is produced, but how much of it gets into your home and how much of it gets diluted or escapes. Summer conditions in Georgia, with sealed homes and humid soil, can be quite effective at delivering radon into your living space.

Counties like Fulton, Gwinnett, Cherokee, Forsyth, and Cobb sit on geology that produces moderate to high radon levels. If you live in any of these areas, summer is not a safe time to assume your radon levels are low without testing.

If you have been putting off radon testing because you heard summer is not the best time, now you know that is not accurate for Georgia. Here are some specific situations where a summer test makes perfect sense.

When you receive your summer radon test results, here is how to think about them in the context of seasonal variation.

If your summer result is above 4 pCi/L, you need mitigation. There is no seasonal caveat here. A reading above the EPA action level at any time of year means your home has a radon problem that should be addressed.

If your result is between 2 and 4 pCi/L in summer, consider retesting in winter. See our guide on radon levels in winter vs summer for more on seasonal variation. Some homes in this borderline range will test above 4 pCi/L during the colder months when the stack effect is stronger. Having data from two seasons gives you a more complete picture. Learn about your options in our short-term vs long-term radon testing comparison.

If your result is well below 2 pCi/L, your home likely has low radon risk. This is encouraging, though the EPA still recommends retesting every 2 years to account for changes in your foundation and soil conditions.