First, is it important to the story, and if so, why? Tell us only what we need to know about the rain. If it’s just setting a mood, we don’t need much. If you want to practice your descriptive skills, great, do that, but don’t expect to hold a reader’s attention with a protracted nature report.
One earnest but misguided writer I know applied the guidance to “show, don’t tell” wholly and indiscriminately. He included a lengthy scene detailing the receptionist’s filing of her nails, one by one. He wanted to show she was bored and ignoring the waiting visitor. She made no other appearance in the story, and her nails were of no importance at all; she wasn’t going to break one and leave the fragment at the scene of a crime.
Guess how that scene affected the readers who sat through it while he read it aloud at an open mic.