Nope. The only reason people usually have any trouble when it rains is because they don't wanna go out there and check their pool. Thus, sometimes the chlorine level drops too low and that invites algae. The only other thing that sometimes can happen is that your ph may drop some if your area has acid rain. But, to answer your question about do you need to do anything ahead of time? Just test and adjust after the rain like you thought.

I think you are well on your way to knowing how to handle your pool. Congrats on a job well done. Glad we were able to help get things under control for you. Enjoy and good luck.