I bike from April to December in my Canadian city.
In the spring and late fall it rains. A lot.
If it's warm, I just get wet and don't sweat it.
If it's cold, like it was yesterday and today, I bundle up with cycling pants (not waterproof), a jacket over my cycling jersey and arm warmers, put on shoe covers, and air out my gear in my cube at work with the fan going. I haven't hit a downpour that a fan and 8 hours can't dry!
And best of all, every time it rains, traffic STOPS. I get to work faster and in a better mood than if I drove.