Personally I don't think it's worth messing with your tire pressure during rainy weather, just keep your foot out of the throttle and drive with caution. That or get some of those badass 7" wide chrome casino rims and just cut through puddles and mud !!!!!
Quick Time Perfomance carries them, the have some videos on various applications & product info on their website. http://www.quicktimeperformance.com/QTEC/index.html