I was flying a Cessna 340 out of North Las Vegas during a winter storm, filed IFR for San Diego (KSEE). The controllers were very busy and I was given an initial altitude that put me 1,500 into the clouds. I noticed my weather radar (older black and white one) was painting all white ahead (big cell with lots of moisture). I kept trying to call control for a heading change, but they would not respond. I just knew the cell would be full of ice, hail, and hell so I repeatedly to pushed the ident button on my transponder and started to turn away from the cell. Soon control came on and said, "62C I see you are turning away from that level 4 cell", I thought yeah, thanks for the help and obviously you were going to let my flying into that!. I immediately asked for 2,000 ft lower and told them If I could get that I would cancel IFR, request immediately granted.