heres the question-which value are you calling your "memory voltage"? on my setup I have "+5Vsb"=4.97, "+12" = 11.770, "+5" = 4.86, "+3.3" =3.13 and "VcoreA" = 1.720
a couple seem a little low, but I dont know what "VcoreA" is supposed to be.
Then it sounds like you have a different issue. I wouldn't go messing with the memory voltage on your machine in that case. My problem was that after playing for 15-30 min I would get a high pitched sound out of my speakers and then it would BSOD. I don't believe I ever had that rain/thunderstorm bug.