If you are a homeowner, you have likely heard about radon. It is an invisible, odorless, and naturally occurring radioactive gas that can seep into your home from the soil beneath your foundation. It is also the second leading cause of lung cancer.
But there is a common misconception that once you test your home for radon, that number is set in stone. The reality is that radon levels are dynamic. They fluctuate from day to day and month to month. One of the biggest drivers of these changes? The weather outside.
Here is a look at how different seasons and weather patterns can affect the radon levels in your house—and why understanding this is crucial for your family’s health.
1. Winter and “The Stack Effect”
Winter is notoriously the time when indoor radon levels hit their peak. This is largely due to something called the “stack effect.”
When the temperature drops, you turn on your heating system. As the warm air inside your house rises and escapes through the upper levels and attic, it creates a vacuum effect (negative pressure) in the lower levels of your home, like your basement or crawlspace. This vacuum literally sucks the soil gases—including radon—up through the cracks in your foundation and into your living space. Combined with the fact that our windows stay tightly shut all winter, that trapped gas has nowhere to go.
2. Rain and the “Capping Effect”
Have you ever noticed how a dry sponge absorbs water, but a wet sponge can’t take in any more? The soil around your home works in a similar way.
During heavy rainstorms, the soil around your house becomes saturated with water. This creates a temporary “cap” over the ground, making it incredibly difficult for radon gas to escape into the outdoor air as it normally would. Seeking the path of least resistance, the gas is forced laterally through the dry soil directly beneath your home and pushed up into your basement.
Note: A frozen yard or heavy snowfall in the winter creates the exact same capping effect!
3. High Winds and Air Pressure
Strong, gusty winds do more than just rattle your windows; they actually change the air pressure inside your home. When high winds hit the side of your house, they can increase the negative pressure indoors. Just like the winter stack effect, this drop in pressure acts as a pump, drawing more radon out of the soil and into your home.
4. Summer Fluctuations
Summer tends to bring lower radon readings, but it isn’t a guarantee. If you are the type to throw open the windows to enjoy a cross-breeze, the natural ventilation will easily dilute the radon gas, flushing it out of your home.
However, during brutal heatwaves when the air conditioning is blasting and the house is sealed up tight, radon can still accumulate. While the “stack effect” is much weaker in the summer, a tightly sealed, air-conditioned home can still trap dangerous levels of gas indoors.
What Does This Mean for Your Home?
Because weather heavily influences radon, a single short-term test done during a sunny, breezy week in June might show completely safe levels, while the same home could test dangerously high during a snowy week in January.
Here is what we recommend:
- Test in the worst-case scenario: If you are doing a short-term test, the best time to do it is during the winter heating season or right after a heavy rain.
- Consider long-term testing: A 90-day (or longer) test gives you an average reading that accounts for weather and seasonal shifts, providing a much more accurate picture of your true exposure.
- Mitigate for peace of mind: If your levels are high, the weather shouldn’t dictate your safety. A professional radon mitigation system works year-round. It actively pulls the gas from beneath your foundation and vents it safely outside, preventing it from ever entering your living space, rain or shine.
Don’t leave your indoor air quality up to the weather forecast. Schedule a free consultation or get started with a free professional radon test.