Ha Nick! I can speak from a recent August trip where I drove in one direction straight from NYC to Chicago with operating A/C, and then had to do the majority of the return leg with the A/C no longer operating. Both drives were at a solid 80-85 mph (where there wasn't construction logjams). When I got to Chicago I was reasonably alert and relaxed. Back to NYC I was tired and shot. I guess it depends somewhat what kind of driving you plan on doing but for me trying to drive at high speed with windows open is not comfortable, very noisy and ultimately very fatiguing.