1999 Q wrote:No codes present. That was my first step.
Lights coming on in the rain isn't a sign of a mechanical problem - it's clearly an electrical issue.
Some say (I've never had it), that the TRAC OFF and ABS lights come on when there is an issue with the charging system (alternator, battery).
I would first suggest having the battery properly load tested and also the alternator at a place with the correct hardware.
My guess is you have a portion of the wire harness that is just shorting out with the rain. Get under the car with a flashlight and look.
edit: Still have your plastic splash guard under the car? Always amazes me how many people don't have those anymore (typically those that get oil changes at 10 min oil joints)