I felt fine during the run, itself, and after the run during the evening. However, after I went to bed, I couldn't get warm. I piled on extra blankets, but I lay in bed shivering. After a couple hours, I went down to my computer room to sleep. I set the house thermostat to the daytime value, and I got warm and slept OK for the rest of the night. The computer room is the warmest room in the house, because it has a heat register just for that small room, and the computer and LAN equipment put extra heat into the room. I nibbled at some crackers for breakfast on Friday, but I didn't eat much during the day. I slept most of that day as well as my normal seven hours last night. I've had a cough for the past week, indicating my body-condition isn't good. That, and the stress of being hungry and running during the coldest night we've had this winter, apparently gave more stress to my body than it could handle.
I think I made some mistakes on Thursday before and during the run. I hadn't eaten much during the day, so when I went running/walking my body energy was low. During the run, the temperature was about 15 (F), and a 10 mph wind was blowing. I wore the same three layers that I've been wearing for temperatures in the 20s. I think I should have added another layer, and I definitely should have eaten more during the day before the run.
I feel better this morning, and I just finished a normal breakfast. My wakeup pulse rate (WPR) this morning was 67, indicating my body is awfully tired. I feel like my body is tired, too. Thus, I'm not running today (tomorrow is my normal rest day), and I'll see how my WPR is on Monday. I may or may not run on Monday, depending how I feel after I get up.