I must admit, I never let weather stop me (except maybe when its above 30C and sunny and humid in which case I will have passed out anyway). If it's wet and cold, put on some rain gear, an extra layer of wool underneath until you warm up and bring a dry shirt for when you stop. No reason to let a bit of water stop you. Just be a bit more careful as you would if you were driving in rain. We have a saying in Norway (which my dad is very fond of): there is no such thing as bad weather, only bad clothes.