I ran the roof air for most of a 2 week trip at 55-60mph and in 90 degree plus heat. It was comfortable inside most of the time, but when it got to 95+ outside, the driver's area was a bit warm from the engine heat leaking in. I had no dash air, as I need a "charge". The air coming out of the a/c unit was ice cold at all times, just was not qiute enough for the extreme heat and humidity. At 85-90 outside it was fine. I also have 2 small 12v
dash area fans that help to move the air quite a bit. They are inexpensive additions.