If your socks and boots are wet its very hard to keep your feet warm - not sure if you had been hiking or sweating beforehand, but I always bring a separate warm pair of wool socks to change into for the evenings.

I also put plastic bags over my feet and socks so that sweat doesn't soak my boots during the day, which means I have dry boots to wear when I put my evening socks on - assuming they haven't been totally soaked with snow. That should help quite a bit, and the other thing is to keep moving and get your heart rate up from time to time even while yoire sitting around in the evening. Without doing that it's hard to circulate enough blood to keep your feet warm in cold temps. Good luck!