Dollar store shower caps (2 in the pack) for 99c cannot be beaten IMO for over the helmet rain protection. My helmet has a visor and the shower cap is just a little tight going over it. This leads to tears. Duct tape. I also have thin skullcaps designed to go under the helmet for warmth. They do not breathe and in the rain or not in the rain my head gets soaked. It is only bad if I take it off because the moisture cools quickly and it is not pleasant having to put a skullcap on wet after it has cooled below body temperature.

H