Rain is the best condition in my opinion seriously I really like riding in the rain, as long as you dress accordingly to the temperature and weather there's nothing to fear from the rain. It took me a while before I did my first commute in the rain because I was afraid but once you do it you know that it's no big deal.
Fenders is a must but for clothing there's a lot of different opinions. I prefer getting wet from rain rather than getting wet from swet so I wear wool when it rain during colder days.