Rain is Neutral usually at 7.. unless its Acid Rain .. Youll find that rain water is much more beneficial than well water as the plants will testify and show such ..
Just remember with rain water you most likely need to supplement it with Cal and Mag. Unless you are using very complete nutrients. But as the others have said, your plants will love it.
I retaced my pervus statment about acid rain, I more or less ment, the earths air is polloted, and when it rains , the pollontates get in the rain drops. I guess i ment all rain is Dirty rain, as the ph is still 7 but it has all the nastyness from the Air.
all rain is not acid rain, but it is not the cleanest