I washed my Ebony VX in the hot sun (water steamed when I sprayed it) and when I was done, I didnt have one single water spot.
In Ohio? Here in the middle of the Mohave we just finished a dozen days or so above 100 degrees. But in Summer it starts to get real hot. Last year 133 degrees. Here in the summer you turn off your water heater to have a supply of cold water cause brushing your teeth with hot water sux. Here you do not wash your car in the summer you steam clean it.
Yeah, it gets sunny and hot here in Ohio.....but about 90+ on that day in the full sun. But a black vehicle just absorbs the snot out of that heat.
I can't imagine how or why you deal with that heat. I couldnt survive.