I tried driving in the a tstorm without the top on, (got caught on the road).  It did not work to well.  The YJ should be fine if it does get wet on occasion.  I did have to repair the circut card behind my gauges a few years ago though.  The previous owner must have let it get wet quite often.  Some of the runs on the card had corroded.  I ended up having to make some electrical jumpers and solder them over the corroded areas.