Generally this takes the form of either an exceptional short lived event, such as the passage of a tropical cyclone or even the rainfall associated with a particularly intense thunderstorm or of a long duration rainfall event with lower intensity, such as the cumulative effect of monsoon rainfall in South Asia.
Usually, this phenomenon manifests as either a brief exceptional event, similar to the impact of a tropical cyclone or the accompanying rain from a particularly strong thunderstorm, or a longer-lasting but milder event, such as the aggregate effect of monsoon rains in South Asia.