I keep a beater bike for bad weather riding. I like riding in a warm summer rain. 32 mm or 1-1/4" tires help. Just be careful on painted road surfaces and crossing RR tracks. And accept that you shouldn't try cornering like Sagan.

I commute in the rain all the time. I've done all kinds of things to make it as comfortable as it can be. We don't really have a warm rainy season here in the Pacific Northwest... you can plan on lots of days with rain and temps in the 40's to low 50's. My latest addition to my commuter/rain bike is a BionX electric motor. So, even if it's wet, I can't complain about the riding being too difficult (pedal assist only, no throttle... but still, PAS level 4... a piece of cake.) My road bike doesn't have fenders... I don't enjoy riding it in the rain. Someday when I get bike N+1... I'll get a nice road bike that has fender mounts. Maybe this?:

Domane 6.2 Disc - Trek Bicycle

Why ride in the rain, I just ride the next day if it's dry. 10,141 miles in 2015 and maybe it sprinkled on me 5 times. I only remember one time when the pavement was wet. Ride leader took us TOWARDS the dark clouds that day for some dumb reason. Turned 90 degrees and it was dry within two miles.

If you live in Seattle or Portland, waiting for the next dry day could lead to a long wait. Fenders prevent a long wait.

I dont mind getting caught in a summer rain. Otherwise, I'm waiting until the radar shows no precip for my area. A few years back I did a November mountain bike ride in 40F drizzly rain and decided not to do that much.

Had to do it last night as the truck was in the shop and they did not finish it. Rode 12.7 miles in a downpour to get home! Was not that bad. At least I had the Trek crosser with me and not the Cervelo. Had my gor-tex suite and stayed pretty dry. I think most of the wetness I had was sweat. Was like riding in a plastic bag.
I rode in this morning and it was wet but no rain

Bill