And even in the most extreme cases, it doesn't do nearly what I thought it would. People often ask if rain will affect their pool's chemical levels, and the answer is always "no." Well, that is not always true. The past 2 days, I got 8.43" (according to my manual rain gauge) or 9.62" (according to my automated gauge) of rain. As you might be able to guess, my levels are not what they were before the rain. I honestly thought everything would be worse, but I'm still going to have to work to fix everything.
Obviously, in just about every case, rain WILL NOT affect your levels. I just posted this, because I thought you might like an example of what extreme rainfall can do. Keep in mind, this was 2-3 months worth of rain in 2 days.