In the rain, I wear as little as possible. I wear what I need to wear to keep from getting cold. If I can wear a short sleeve shirt, shorts, and sandals (and no socks), that is ideal. If it's cold enough to justify wearing pants, I will wear wool dress trousers, because wool stays warm when wet. I keep a spare set of clothes at the office in case I get thoroughly soaked. It doesn't happen often. Other than getting cold, the most uncomfortable thing about riding in the rain is having rain-soaked clothes tug at my body when I'm moving. This is why I prefer to wear as little as possible.