My view is that you're not going to stay dry, so don't think about it that way. Just stay wet and warm. I don't wear anything waterproof, just wind resistant. Thus I wear the same clothes raining or not, just another layer in the rain. I don't tour when weather is going to be miserable, so I don't take rain pants or even tights. Leg warmers are fine. Craft undershirt, short-sleeve jersey, arm warmers, wind jacket, wind vest, shoe covers. Light stuff that dries quickly. With that gear, I'm good down to about 45° and raining. If I get cold, I pedal harder. I don't mind riding in the rain. I'd rather ride in the sun, but it's fun either way. The bigger problem is what to do with your wet stuff when you stop for the night. The less of it you have, and the less water it absorbs, the better. I haven't used wool in 30 years for that reason.