On really wet days on top of my usual gear (Half-buff under helmet, MIPS helmet, downhill long-sleeved shirt, shorts, knee/shin guards, merino wool socks, 510 shoes), I wear a Patagonia Torrentshell jacket, Montbell PreCip pants, and VBL socks.

I'll swap my sunglasses for clear plastic safety glasses because I don't like rain in my eyes and always get mud in my eyes on downhills.

The pants are a little baggy so I'll need a velcro strap around the ankle to keep them out of the gears. With the buff under my helmet I don't usually use the hood of my jacket unless it's really pouring, but the jacket is fitted for use with climbing helmets and almost covers all of my bike helmet. There is a dedicated WP/B helmet cover but I haven't felt the need.

I have a Camelbak rain cover for my pack but also a seam-sealed sil-nylon liner bag I put everything in inside the pack. I'll use the rain cover alone for light rain and both for heavy rain.

Then there are the fenders. I have three. Mucky Nutz under the fork, the Grand MOM in the back, and another up the downtube. None of these do the job. I get mud on my face, I get mud up my back and under my seat, and I get muddy everywhere.

For drizzle and light rain I'll just wear the Torrentshell jacket and even leave the pack uncovered. My wallet and phone and many other items (first-aid, repair kit, notebook) are covered in hand-sewn sil-nylon bags anyway and the pack has several layers so it would take a lot to get soaked through.

If it's in the 30's I'll wear my Salomon cross-country ski pants, and I have a medium weight Patagonia long sleeved insulating layer and a synthetic t-shirt. I can wear both or either. And a double layer of socks is usually sufficient. If it were much more below freezing I'd be more careful, with a size larger pair of shoes just for the winter, insulated/reflective insoles, and thicker socks.