What weather conditions are most likely to cause spikes in indoor radon concentrations during testing?

Severe storms or high winds can significantly affect indoor radon concentrations. Under such conditions, changes in atmospheric pressure can lead to variations in the building's air pressure relative to the outdoor atmosphere. During storms, the outdoor air pressure can drop, which may result in the infiltration of radon gas from the ground into homes through cracks in foundations, gaps around pipes, and other openings. This influx can be exacerbated in buildings with poor ventilation or high levels of moisture in the air, which can trap radon indoors.

In contrast, other weather conditions like unusually mild weather, normal sunny conditions, or moderate rainfall typically do not create the same pressure differentials or conditions that lead to increased radon infiltration. These calmer weather patterns are less likely to disturb the ground or pressure balance, making them less associated with spikes in indoor radon levels during testing.