Radon levels in your home can change depending on the season. This is why year-round radon testing is so necessary. In winter, radon levels often go up because homes are sealed tight. In summer, you might think radon levels go down—but that’s not always true. Some homes have higher radon in warm weather, depending on how they’re built and where they are.
In this article, you’ll learn why radon levels change with the seasons. We’ll talk about why radon is usually higher in winter, why some homes have more in summer, and why every home needs testing in different seasons. We’ll also explain what you can do to keep your family safe year-round.
If you’re wondering when to test your home or how to protect against high radon levels, this guide will help. Radon is the second leading cause of lung cancer, so testing isn’t just necessary—it’s life-saving.
Let’s look at what causes these seasonal changes and how you can stay protected.
What Causes Higher Radon in Winter?
Radon gas comes from the soil under your house. In winter, cold weather affects how this gas moves. Here are some reasons why radon levels are usually higher in colder months.
Your home is closed up tight in the winter. You shut your windows and doors to keep heat inside. But that also traps radon inside the house. Less fresh air means radon has nowhere to go.
There’s also something called the stack effect. Warm air rises and escapes through the top of your house. As that warm air leaves, it pulls in cooler air from the ground—and with it, radon. This vacuum effect increases the amount of radon that gets pulled from the soil.
Frozen ground can also trap radon under the surface. That pressure pushes more gas into your home through cracks and openings in the foundation.
So even though you might not feel the cold indoors, your house could be pulling in more radon than usual.
Why Are Radon Levels Sometimes Higher in Summer?
Summer radon levels are usually lower, but not always. Some homes actually have reverse seasonal patterns with higher levels in warm months. That’s because of how air moves, how houses are built, and where they’re located.
In many homes, people open windows and doors during summer. That lets radon escape, and fresh air comes in. This natural ventilation can keep radon levels low.
But not all homes get that airflow. If you use air conditioning, your house may stay closed up. Air conditioners can reduce the amount of fresh air that comes in, just like in winter. This can keep radon trapped inside.
Also, in some areas—especially hillside homes, south-facing buildings, or places with volcanic soil—radon levels go up in spring and summer. These homes may become hot inside, and changes in air pressure or soil gases can allow radon to enter more quickly.
Sometimes, radon spikes suddenly during warm months. If you only test in winter, you could miss these dangerous jumps in summer.
What Types of Homes Have Summer Radon Spikes?
Some homes are more likely to have high radon levels in summer. These include:
Homes are built on hillsides, especially in the lower parts. The slope affects how soil gas flows around the house.
South-facing homes that get a lot of sun. Solar heat affects indoor temperatures and pressure, which can increase radon entry into buildings.
Homes in volcanic or rocky areas with high soil radon. These areas naturally release more gas.
Buildings with tight construction or poor ventilation. Less air movement means more radon gets trapped.
Homes with basements or foundation types that make it easier for gas to enter through cracks or soil contact.
If your home has any of these features, summer testing is even more critical. You can’t assume radon will be low just because it’s hot outside.
Why Is Year-Round Radon Testing So Important?
Radon levels change not just with seasons but with weather, building materials, and even how often you open your windows. That’s why it’s not enough to test just once or only in winter.
Year-round testing shows the whole picture. If you only test during one part of the year, you might miss a season when your radon levels are dangerously high.
Newer studies indicate that radon levels can remain elevated throughout the year in many North American homes. In some cases, radon levels don’t change much with the season. In others, they spike without warning.
Testing in both summer and winter gives you the best data. If one test is low, the other might show a different story. You need to see the full pattern to know if you need a radon mitigation system.
Experts also recommend retesting every two years. That way, you’ll know if anything has changed due to new construction, landscaping, or weather changes. Even a slight shift in your home or yard can affect how radon enters.
What Can You Do to Reduce Summer Radon Spikes?
If summer radon spikes are a concern, you can take steps to lower your risk. Improving your home’s ventilation is a good start.
Open windows and doors when the weather allows. Use fans to help move air out of the basement or lower levels. More air exchange means less radon gets trapped inside.
If you have a suspended floor or crawlspace, mechanical under-floor ventilation can help. It reduces radon before it gets into your living space.
Some homes need more advanced solutions. An active radon sump system with a fan pulls radon from under your house and vents it outside. This works for most foundation types and is one of the most effective fixes.
Construction techniques can also help. Using a gas-permeable gravel layer under the foundation allows radon to flow away from your home. Covering that with heavy-duty plastic sheeting adds a second layer of protection.
Sealing cracks and gaps in the foundation stops radon from sneaking in. Adding a radon vent pipe from the ground up through the roof helps direct the gas outside rather than into your home.
Combining these strategies gives you the best protection. Just remember, no solution works unless you know your home’s radon levels first.
How Often Should You Test for Radon?
Experts suggest testing your home at least once every two years. Even if your home tested low in the past, things can change. Soil moisture, weather patterns, and home renovations all affect radon levels.
If you’ve never tested your home, now is the perfect time. Start with a long-term test if possible—it gives a more accurate average over time.
Already tested in winter? Do a follow-up in the summer. Already tested in summer? Try again in winter. This way, you’ll catch any seasonal spikes and know if you need a fix.
If you have a radon mitigation system, test it regularly to ensure it remains effective. Don’t assume the system is handling everything. Verify it with data.
Why You Shouldn’t Trust Just One Radon Test
One radon test isn’t enough. A short test might catch low levels on a good day and miss dangerous peaks the next. Radon isn’t always steady—it can change from hour to hour.
If you only test once and only in one season, you might get a false sense of safety. That could put your family at risk.
The best way to stay safe is to test in multiple seasons. That provides a comprehensive view of your home’s air quality and helps you make an informed decision.
What Should You Do Next?
If you haven’t tested your home for radon, don’t wait. Summer might seem like a low-risk season, but that’s not always true. Your home could have hidden radon spikes right now.
Start with a test. If levels are high, talk to a radon mitigation expert. Ask about improving ventilation, sealing cracks, or installing a sump system.
Radon testing is simple, fast, and affordable—and it could save your life.
Get more information, request a quote, or book your appointment today. Don’t let seasonal changes hide a year-round risk. Protect your home and your health now.
