I forgot to mention, when I did the 5K, I wore long undies and long running pants with some calf sleeves and wool...

I forgot to mention, when I did the 5K, I wore long undies and long running pants with some calf sleeves and wool socks. My feet and calves were completely warm. My butt got cold toward the end. I definitely wanted the neck buff thing to pull over my face most of the time, but it got a little warm on my neck toward the end. I can't quite figure out what I think of the top layers. I needed them until around the end of the 2nd mile. After that, I'd have liked to take off something, but I'm not sure what. Using the wool glove liners inside the gloves was key. It made it easy to take the heavier gloves off when my hands got warm, and then the thin wool was perfect by itself. I had a wool cap on, and that was a good idea in that cold. I mean, I'd have liked to get away with just a headband for my ears, but I know I would have had a horrible headache from the cold if I had not had the full cap.

So thank you for all the gear suggestions. They worked really well. There's no accounting for the fact that my butt fat failed to insulate me properly.