I have been having issues with my 07 pilot having the vtm4, abs and vsa lights come on when driving in the rain. Once it dries out the lights all turn off. It drives normal other than the systems being off.
Having those lights come on has often been a sign of a weak battery or alternator. These Pilots do not tolerate weak charging systems very well. Having the lights come on only when wet is a bit different, but perhaps it's because you are also placing an extra load on the electrical system (headlights, wipers, etc.).
The problem could also be caused by something else entirely, but checking the battery and alternator is an easy first step. When those lights came on in my 08 they were very consistent (wet, dry, all the time), and it turned out to be a battery that was getting weak.