Today was a two-layer day

The shade temperature during my run was in the low 40s (F), and it was probably in the high 40s in the sun. I wore two layers, my summer poly T-shirt and my nylon jacket. I was cold during the first couple of miles but felt fine after that. During the latter part of the run, I unzipped my jacket to keep from sweating. Sweating is a sign of energy being wasted.