My very first autox it rained very heavy at start of race, tapered off but still rain all day. My SVTF did really well in the wet, especially compared to the rear wheel drive cars. The front wheel drive do pretty good in wet weather (if you have decent tires). If you know how your car handles in the rain and it's limits you'll do fine. I think all the responses given here covered about everything. What helped me the most was talking to other experienced drivers at the event. Don't expect much and have FUN. This sport is about seat time, the more seat time the better you'll get. It's definitely addicting and a lot of fun seeing what your car can do.
2007 Mazdaspeed 3 GT: TurboXS DP/RP, CP-E SRI, Forge BPV, SU rear MM/solid shifter bushings.
2004 Silver SVTF ZX5: JRSC, MBRP, FRPP Multimatic suspension, Progress 22mm RSB, stage 2 TB, Steeda STS, CFM rear MM, Black OZ Evo's.