Solar Powered Runner

Last Friday, I tried a predawn morning run, about 3.25 miles around my neighborhood.  I wore a cap with an imbedded flashlight in the visor, which was important because some of the street lighting where I live leaves a lot to be desired.  It was a pleasurable experience.  I could see the stars clearly, even including my favorite, Canopus, which was peaking low above the southern horizon.  Yes, I liked it.  And I felt the same degree of energy I usually have during my late morning runs.  But get this: my final time was about a minute slower than when I run the same distance in the middle of the day, under much warmer conditions.

Then early Sunday evening, as the skies were gradually darkening, I ran the same course.  Once again, I thought I was pacing myself like I usually did and felt energized.  But also once again, my time was slower than usual.  In between and after these two runs, I ran in the middle of the day.  I perspired more and it was less pleasant, but I ran faster nevertheless.  So I wonder...

Does exposure to the sun have some kind of positive effect on my running, making me faster?  Am I a solar-powered runner?  This would seem to run counter to the conventional wisdom, which states that I would be better off under cooler nighttime or twilight conditions.  Of course, indoor treadmill running is away from the sun.  But with that, my pace is set by what I enter on the machine and not by my inner sense of how fast I'm running.

Despite my puzzling slower pace at night, I'd like to do more nighttime runs.  The streets are pretty deserted in my neighborhood between 5 and 6 AM, so if I can just rouse myself up and hit the pavement, I should be able to pull this off...