Not totally sure why you would want to fly in the rain for two reasons:
1. you’re going to be drawing moist air into the drone and over the electronics, not sure that’s an idea that will prolong the life of the drone.
2. Photographs are going to be blurry, try driving in a car through a rainstorm without wipers!
Yes you can buy a “wetsuit “ for the drone, it’ll cost you, but bearing in mind the two points above, is it worth it?
Hope you’re enjoying the flying, take care and catch you later. Peter.