Riding in the rain should not be frowned upon. In fact, it’s one of the rules:
Rule #9 // If you are out riding in bad weather, it means you are a badass. Period.
Fair-weather riding is a luxury reserved for Sunday afternoons and wide boulevards. Those who ride in foul weather – be it cold, wet, or inordinately hot – are members of a special club of riders who, on the morning of a big ride, pull back the curtain to check the weather and, upon seeing rain falling from the skies, allow a wry smile to spread across their face. This is a rider who loves the work. (Taken from http://www.velominati.com/the-rules)
I find that riding in the rain is oddly satisfying and is necessary to graduate to the next level of suffering. Most (sane) people want to stay inside when it is pouring but I love the tranquility of empty roads and the rhythm of a steady downpour.
It is common belief that riding in the rain requires a significant amount of extra gear but in reality, a simple rain jacket over your existing fall/winter gear is more than enough. On a rainy day, I’ll usually wear a base layer, jersey, wind vest and a thin rain jacket. The jacket doesn’t offer great ventilation but offers a certain level of water resistance.