During mid-day, I drove to the 100th South trail head and went south on the Jordan River Parkway. I ran for about 55 minutes (2 miles). Most of the path was clear, but in the shady spots, there was about 50% ice and 50% asphalt. The temperature was in the high 20s (F), and a slight north wind was blowing. I wore 3 layers, and my body felt fine, but my fingers were cold. When I was in marathon training, it would take about a mile and a half for my body to warm up. Now that I'm older and am walking as well as jogging, it takes longer for my body to warm up. The pain in my fingers was just beginning to subside when I got back to my car, even though I had cotton gloves that provided protection against the cold.
This picture, taken from the web, shows fingers that have frostbite and are thus white due to poor blood circulation. My fingers were cold today but did not have frostbite. However, I have a pair of heavy mittens that would keep my hands warm, but I
haven't been using them during my running due to their weight. I'm going slow enough that the weight of gloves shouldn't be a concern, and I think I will use those mittens on my next run if the temperature is in the 20s or below. The mittens have about 1/4 inch of wool with a nylon shell.
I used to do a lot of winter camping as Scoutmaster, and I only remember one time when two or three of my scouts had problems with frostbite. I taught them to check their faces and hands often for frostbite and to check their toes when they first got up, the symptom being small white spots on their hands and feet that indicated frostbite was beginning to occur. One morning after we got up, a couple of the scouts had small white spots on their toes. My car was nearby, and I took the affected scouts to the car and used the car heater to warm them up. I had taught the scouts to use hand warmers in their sleeping bags to keep their feet safe while they were sleeping, and most of the boys were OK.