pluvial
adj. relating to rainfall

A little tap at the window, as though some missile had struck it, followed by a plentiful, falling sound, as light, though, as if a shower of sand were being sprinkled from a window overhead; then the fall spread, took on an order, a rhythm, became liquid, loud, drumming, musical, innumerable, universal. It was the rain.

— Proust, Swann’s Way