[Munch]

As far as rain gear goes…nothing over the top, simple… frogg toggs is what I use…. they are pull overs. I keep them in my saddle bags all the time. Here in the south… an afternoon rainstorm is all but guaranteed. You will have a rather short riding season if you let rain stop ya. As far as hydroplaning…. I have yet to get mine to do it…just slow your speed a touch and you should be good. Your tires are more pizza cutters for water then a cars tires are. Just stay in the left tire track of the car in front and drop that 2 second following distance to about 5+ .You will need to watch painted spots and steel covers, grates, draw bridge segments etc too if you plan on turning.
Other then that… the riding is the same for me. Visibility only gets limited if your following too closely. That and I use a water repellant on my face shield.