Originally Posted by Alan K

During very cold weather, I do not bicycle more than 2 hrs. I have learned that you must have an outer layer that prevents air from stealing your body heat otherwise it becomes a losing battle. Once the temp dips below zero, I have a pair of almost knee heigh compression socks (fully cover calf muscles), a layer of thin wool blend socks, and finally a thicker wool or one of the newer blended materials that does not trap moisture, should you get a little warm. I also use wind proof shoe covers that seal the shoes completely by a zipper and a chord at the top that goes up to ankle. The last layer has proved quite beneficial at and below zero F. Should the temp rise and I feel a little warmer, I can always unzip the shoe cover partially to ensure that moisture doesn’t condense. Without all these layers, my feet do get cold and I don’t like the idea of riding too long when my feet or fingers are beginning to approach numbness, even if I can push for a while longer.
Decades ago, when I experienced my toes going numb the first time, I found a coffee shop to get warmed up - a hot cup of coffee and a warm brioche never tasted so good. After that a number of well thought purchases were made to survive the winters.

Good luck, and keep warm!