What to Expect

[CarlD]

So a sudden in flux of cold water, rain, won't throw my numbers out of whack?

Who knows? Most likely, pH will drop, especially if your area has slightly acid rain. Cold water will only throw your temperature out of whack.

You may see some dilution if you have to drain off water. This can lower CYA, T/A, Calcium, and, of course, Chlorine.

Rain happens. Its debris that's more the problem.