Click the ground to call the lightning down there: the flash is instant and throws every shadow at once, and the thunder arrives later the further away it struck. Turn the sound on.
The rain is 1,400 streaks of useHelperLines, and the splashes a particle emitter spread over the street (the era's trick: they are not where the drops land, and nobody can tell). The bolt is a jagged line, and the sky is the one light that casts, flashed for a tenth of a second.
The thunder and the rain are synthesized by the example, sample by sample, as WAV files loaded with useLoadAudio.