When my commute was longer, I took a full change of clothing to work. There was no need for a shower as long as I was reasonably clean to begin with. A quick wipe-down and change of clothing and I was fine.
I have a rain jacket that is so old I have no idea what brand it is. It has pit zips which are permanently unzipped. I wear rain pants in the rain. I have two nice goretex (or similar) rain pants, with good vents and whatnot, and I like to ride in them especially in fall and early winter when there's a lot of leaf muck on the roads. Even though I have fenders I still get messy. I don't find them hot, but my commute isn't very long. Disclaimer: I am a dork.