cloudburst

kaatosade A sudden heavy rainstorm.
1899, w:Edith Wharton|Edith Wharton, "A Cup of Cold Water" in The Greater Inclination:

But the sound . . . expressed an utter abandonment to grief; not the cloud-burst of some passing emotion, but the slow down-pour of a whole heaven of sorrow.

A cloudburst in the China Creek district followed by continued heavy rains was responsible for the increased water.

In Uniontown, Pa., John Walchesky & family rushed from their house when lightning set it afire, rushed in again when a cloudburst put out the blaze.

He walked across the lawn, wet from a fleeting late-afternoon cloudburst, the first rain in a month.