Understanding the pattern of environmental radioactivity is important for several reasons, for example for the detection of man-made radioactivity. Environmental radioactivity measurements are highly
volatile, making the identification of patterns a challenging task. Analyzing time series of daily radioactivity measurements from eight places in Germany, we show that patterns become visible by means of wavelet analysis. In addition, frequency aspects of weather data, namely precipitatin, relative humidity, and temperature, can be analyzed jointly with radioactivity measurements using cross-wavelet
analysis. We show that even though environmental radioactivity does not follow an annual periodicity everywhere, temperature is in phase, and leading, radioactivity in a majority of the places investigated. Our analysis can potentially contribute to a location-specific definition of maximum permissible radioactivity levels.