I commute every day including light to medium rain days. Last "winter" rain season I don't think I missed riding the bike on any work days because of rain. Even worse than rain days are heavy fog drizzle days which can occur in spring and even early summer. That creates a gritty, wet sludge that can coat the chain with crud. I have full coverage SKS fenders on both of my commute bikes, and leave them on year round. I bike commute daily but I sure don't want to clean my chain that often, or even once a week. With fenders, my chain is good for about 400-500 miles between cleanings. The front fender with mud flap extension blocks nearly all of the junk that the front tire would otherwise throw onto the chain, bike, lower headset and me. Did I mention I have not changed my Shimano Ultegra headset in 7 years / over 30K miles of use? Thanks, fenders.