I could tell, when I got up, that I was tired; I didn't have that "spark" of energy that I usually have. My wakeup HR, though, was 51, indicating my tiredness probably isn't serious, i.e. not another cold coming on. I left on my run, but at 3 miles I turned around and came home. Best that I let my body rest. Hopefully, I'll feel better on Wednesday.
The weather was cloudy with a 5-7 mph headwind, and the temperature was about 30F.