One of the earliest apps I installed, back on the first iPhone, was the Sleepmaker Rain / Storms app. These days it's free, because the owner could no longer make money in the modern app store. I've been listening to the same rain sounds for close to twenty years now. Rain recordings through a phone are often too high-pitched and listening to your rain sounds, all other than two have the same issue; they had a great balance of types of rain sound.
OP, consider syncing with them? You have a slick interface; they have a wonderful audio library.