Rainwater can be highly radioactive due to high levels of radon and its decay progenies Bi and Pb; the concentrations of these radioisotopes can be high enough to seriously disrupt radiation monitoring at nuclear power plants. The highest levels of radon in rainwater occurs during thunderstorms, and it is hypothesized that radon is concentrated in thunderstorms on account of the atoms positive electrical charge. Estimates of the age of rain drops have been obtained from measuring the isotopic abundance of radons short-lived decay progeny in rainwater.