Diesel fuel spills are the greatest concerns if it's the first day of rain (start of rain). It'll become like an "ice rink" for motorcycle.
If it rains half of the day or more, then that's the least of the worry.
But here's the thing is that it's not always on highway. It's commonly around the intersections.
For ordinary wet weather riding, I usually ride carefully and everytime I turns, I slow down to 1st or 2nd gear to proceed. I know that my bike's rear and front tires are thick, It's just that I don't know if I would trust Metzeler tire thread
Cuz it's mostly smooth with some groove. I read many of owners who have Metzeler tires like mine give 5 stars ratings on wet road riding. I don't always trust that comments unless I see that for myself with what Jiro say "wear a full armor suit" and ride it
Catty