I did *not* get lucky with cloud cover today...and it was really sunny & hot (when I finally got started at 1:15 pm...).
I (very slowly) ran the whole 2.6-mile uphill to the Spring Brook / Goshawk Ridge junction, but then I stopped to catch my breath (huffing & puffing with hands on knees, etc.) and I walked the remaining uphill section (about another mile).
There were very few other people on the trail -- they were probably smart enough to avoid the heat. :-P