When I reached the 1.75 mile marker, I could tell I was tired, and I turned around and headed back. This gave me a 3.5 mile run instead of the 5 miles I had planned. I'm not surprised that I was tired today since I only had four hours of sleep the night before last night plus an hour nap yesterday afternoon.
The temperature during my run was in the low 80s (F). My wakeup HR was 52, a 4% increase from yesterday. I timed the last half-mile at 11:48, and that pace was typical of the whole run.