what is the ph of normal rain and at what level does it become dangerous?

Answer 1

The pH of normal rain ranges from 5.6 to as low as 4.5 due to natural sources of acidity. Acid rain is therefore typically defined as rain with a pH lower than 5. A pH below 5 is also the point at which fish eggs become unable to hatch, which is one of the more sensitive effects.

Answer 2

5.6 is normal pH of rain.
Good website with an actual graph showing when acid rain begins to affect fish V
http://www.elmhurst.edu/~chm/vchembook/190acidrain.html