For reference, the weather at 3:00 pm on July 2nd was:
Source: Crete Historical Weather
- temp - 27 degrees (about 81 degrees F)
- feels like - 28 degrees
- sun with some cloud
As a resident of southern Ontario Canada....that is a temperature that many people would run in, and think nothing of it. And, we often have higher humidity.
So I don't think it's shocking that she would go for a run/walk that day and I don't think it would be enough to cause heat/sunstroke, considering she ran the day before, with no terrible consequences. (It was a couple of degrees cooler the day before though.)
Of course it is possible that she pushed herself too much on the hills, and the sun could have been very intense. So I'm not ruling it out.
It quite possible that she was at an isolated stretch of the road, someone pulled over and grabbed her. That's what happened with Mollie Tibbetts. She was jogging and alone, grabbed, thrown in the trunk of the vehicle.