Time series of thunderstorm activity at territories of Western Siberia, Kazakhstan, and Germany for the period from 1936 to 1995 have been analyzed statistically. To reveal periodic components in meteorological series, visual observational data of hydrology and meteorology services have been used. Periodic changes (cycles) in the thunderstorm series have been found for each territory under study. Long-period (18 years and longer), medium-period (from 7 to 10 years), and short-period (from 2 to 6 years) cycles have been revealed.