poolgirl22 said:
Its free for me.
That makes it perfect.
I'm with you there!
Rain typically has very little effect on things as it is fairly inert. If anything, it tends to aerate a little bit (pH goes up slightly). The biggest problem for people if they get
lots of rain and don't have enough chlorine. Rain does carry a goodly amount of organic contaminants and so FC can go down pretty quick. Left unchecked, you can get algae in short order. But if you maintain your pool well and keep the FC at target, you'll be alright.
If I see rain coming on the radar, I will often bump the FC a tad before it makes it to me. But then, I'm a geek like that.