One summer many years ago, I was on a trip with three other teenage buddies in the Sierra. We camped in a nice meadow and it began to rain. No big deal, this is the Sierra, it never rains for long in the Sierra in the summer - just afternoon thunderstorms. Three uninterrupted days of rain later, the meadow was a bog, our tarps were no longer really pitched so much as draped over us as the stakes had pulled out of what was now just mud, everyhing we had was soaked - and I mean everything - even the M&M's in my trail mix had the color running off of them. We packed up our stuff - I can still remember squeezing the quarts of water out of my down bag as I stuffed it - and walked down a nearby forest service road to Hwy 89 and a couple miles further into Tahoe City. Found a laundromat and dried out. I recall that my hands were so cold that I couldn't get my money out of my wallet or operate the vending machine for that much-desired candy (fortunately my friends helped me). I know now that we were probably heading for hypothermia, and that a little south of us and at a higher elevation, a couple people died. Lessons learned -
1) meadows look nice but they are crummy places to camp if it really rains
2) the usual weather patterns are not the only possibilities - be prepared to deal with worse than usual.
3) If your situation gets bad, do something about it sooner rather than later
4) never hike ten miles in soaking wet jeans - the inside of my thighs were rubbed raw
5) those M&M's will stand up to some amazing abuse and still taste great.