I think the ambient temperature is not factored in about the high water temperature you are experiencing. If you have been driving this car around during nature's "hot flashes," (sorry ladies, I was always told nature was...."Female") and the engine never overheated so far, I would not worry about it. You have yet to be straded on the side of the road, caused by a, "boil over.....right?"
The second part about letting the car sit while running stationary... is not healthy. The fan helps. But basically, a car's engine is designed to be cooled by the radiator, and by driving through moving air. Most car radiators are small in size because they run efficiently with the designed capacity, material used, and moving air through the car's frontal openings.
For example... most motorcycles engines do not need radiators, because the moving air is the cooling agent.
I'm not trying to be smug here, but if you go back to your general high school physics, you will understand how an engine works. Not only that, but you will never be snowed again by a mechanic's explaination. You'll know the difference.