https://www.pcgamer.com/skyrim-super-realistic-rainfall-mod-brings-beautifully-awful-weather-to-tamriel/

As reported by Sam Horti over the weekend, this mod turns Skyrim into a tropical rainforest. PlayerTw0's wonderful Real Rain SE, on the other hand, turns the climate controls in the opposite direction—giving us realistic rainfall like never before. 

With the simple goal of making rain "as real as possible", Real Rain overhauls the game's rain textures to become more random and natural looking, "while making the rain denser without any FPS lag or bloated save files."