Newsflash: It's summer, track and field is a summer sport and there are more events than the 10k that don't mind the warmer conditions vs. cooler conditions.
The 10k's are scheduled for 8:20 & 9:00pm tomorrow evening. The sun will have already dropped below the west side of the stadium and the trees outside of that so it shouldn't be a problem. Racetime forecast: 80 degrees, 30% chance for scattered thunderstorms, winds SSE @ 13mph. Not ideal, but doesn't sound all that bad to me. Athletes that prepare for all possible race conditions for such an important race are usually prepared. They'll be tactical anyway.
I do think it's funny that the schedule indicates at 9:25pm "End of Day 2" so even the officials think it's going to go well.
A couple years ago at the NCAA meet in Des Moines, it rained a lot and the meet was interupted several times with lightning delays but the times were very fast across the board.