I don't warm up just do stretches. I ran a half marathon this morning with a temp. of 5C, calm and blue sky, elevation over 5,000 feet. Still wearing t shirt and shorts, excellent running weather!!
probably LV ching lived in the States for a long time & has adapted to the cold weather. In HK, I think 15-18C is considered as best weather condition.
We haven't seen clear & blue sky for many years here.