When the rain actually starts, extraneous sounds are banished, along with excessive light. A heavy downpour produces a dynamic variety of white noise, which, unlike mere static, fluctuates in intensity, with each pelting sheet; while lighter rain serenades us with the patter of individual drops. In either case, the effect is calming: it muffles external clamor, and it also harmonizes us to more natural rhythms.
I remember when I was a boy, if ever we were out driving in the rain, upon our return home, Dad would turn off the engine, and the wipers and radio would fall silent, too. Before running for the house, we would always sit for a moment, listening to the gently drumming rain on the roof. Nothing else was of any concern, during that precious interval.
Is the rain a mantra or drone that, in focusing our attention upon it, diverts us from our travails and other vexations? If so, I can imagine nothing as efficacious.