This is more of a curiosity question and to see if other people have experience this. The PH in my tank used to run 7.8-8.0 until I ran my skimmer intake to the outside. My tank now typically runs between 8.1-8.3. I have noticed that when we have rain over a couple of days, my PH drops to 8.0. When the rain stops, my PH climbs again to 8.3 the next day. Just curious if this happens to anyone else and why it happens?