summer time you are far better sucking air from a space in the house that is shaded rather than a window if its hot out side your pulling hot air into the room this just adds to the heat all ready in there,
I pull from a well shaded hatch in the loft space,and i never vent direct through a window,beast man in choppers and all that,i vent down a stair case then a second fan at the bottom pushes it across the landing and out a other window.By the time it reach the window its cooled a lot
Im lucky because my trade is joinery so i can hide all the duct work either by boxing it in or under flooring so it comes up through vent in floor then oss fan pushes it through window