I once ran an old home days 5K in some small town where I was summering with relatives. There was a water table around the first of about 75 turns in the race, about 100 yards in, People were stopping to drink, so I did too. (I was 12 years old. They were not. I figured they knew what they were doing. I was maybe 70 degrees.)
In a more sanctioned type of event, I have seen fluid stations 1K into a 10K. After that there were, curiously, no other aid stations before the halfway mark.