Answer to Question #7178 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
There are seasonal changes in background radiation levels. For radionuclides in the soil the radiation exposure depends on soil moisture. The more moisture, the more the radiation exposure is attenuated (reduced). In winter there may be snow cover, which essentially interposes a water shield between the radionuclides in the soil and persons above it. These factors are the largest variations in background radiation exposure that are normally encountered.
Cosmic radiation varies over a well-known 11-year solar cycle, but this would not be noticed from season to season. An increase in atmospheric pressure will cause the cosmic radiation exposure to be reduced somewhat. This can happen on a timescale as short as a few hours or days. It is not a very large effect at any particular location. The largest effect on cosmic-ray exposure is altitude. The higher you go the less shielding there is from the air and, therefore, the higher the exposure.
Solar flares can cause brief increases of cosmic radiation that can be quite large. However these are somewhat rare and relatively brief events that would not depend on season.
Carl V. Gogolak, PhD