Radon in the environment
The concentration of radon in air depends on the type of soil and on a variety of meteorological conditions such as air pressure, humidity, temperature, precipitation and wind speed. It has been observed that the concentration of radon in air increases significantly after a thunderstorm. The graph above shows the variation in radon concentration over time for the Massif Central region in France. It can be seen that February is the month with the lowest concentration of radon, and October with the highest.
IRSN