If it's raining in the morning, I don't ride. I could, but it's just a comfort thing that I don't. Here on the Colorado front range, most of our precipitation is summer afternoon thunderstorms or snow. If it's raining and warm, I just ride home. I don't ride in the snow either, but that's out of safety concern.
We get a small number of days a year with constant gentle, usually cool, rain. A very small number. Being rare, those days are really nice around here, but I don't ride on such days.