These are events of convective rainfall and, of course, thunder. Aristophanes (450-385 BC), in his comedy The Clouds, said thunderstorms are caused by the banging together of clouds impregnated with rain, like vast sodden fleeces. Nowadays we know that thunderstorms are due to deep convection within cumulonimbus clouds, releasing static instability within at least 3 km depth of the atmosphere.
The likelihood of a thunderstorm depends on three factors:
(a) moist air near the surface, e.g. a mixing ratio above 7 g/kg;
(c) a triggering by surface heating or by confluence due to hills or a front, for instance.
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