For most of the past few months ive been able to handle 4 mile tempos in 5:25 pace and 8 mile tempos in 5:40 pace (on a flat road, usually at night when its cool out)without pushing it really hard. Today I ran a 3 mile xc race in 16:18, which is slower than the first 3 miles of my 4 mile tempo. It was about 80 degrees, a little humid, the course had some tight turns and rolling hills but otherwise a moderate course. I placed pretty well in the race so im not disappointed but my time is still puzzling me. Does anybody know why this might have happened? could it have been the hills, grass, or heat?