How cold and how strong is the wind supposed to be? Are you going to run hard? Or is it more like a training run with easy paced miles?
I ran a training run last weekend in the rain (14.5 miles - 2.5 easy and 12 marathon pace). It was predicted to be upper 30s/40 degrees with rain and a little wind (10mph??). I was dreading it. Considered running inside, but decided to suck it up and run outside with the group. I did the 2.5 miles easy before the group, and it helped me get a feel for how cold it was going to be.
I wore a long sleeve tech shirt, with a very thin lightweight jacket (but it was the most water resistant one I had). Tights (I think my heavier ones, but it might have been my mid weight ones??), and then my running skirt. I wore my gloves, heavier socks and I started with a fleece ear muff. After the 2.5 miles, I decided the fleece ear muff would make me too hot, and I switched to a Bondi Band (headband) over my ears. I also wore a hat to keep the rain out of my eyes.
I pushed the sleeves of my long sleeve shirt up near the beginning of the run. Since it was a harder run, I warmed up pretty well. I was actually very comfortable during the run. I never got too cold. It was mostly a light rain, but we did get poured on a couple of times.
I generally do not like to be cold, and I usually end up over dressing. I think if the conditions are similar to mine, and you are running a harder effort, I think you should be fine!
I hope you have a good race, and don’t worry about it too much. Go out there and have fun!