I know it may be to hard to do, but - OPEN A WINDOW!
As an architecture major, we have a little joke about operable windows, you see, most buildings do not have these things. People thought that we have to have sealed little buildings, not letting any air in or out. Come to find out this is so very unhealthy for both you and the planet. We heat or cool with massive energy sucking systems. There are recently some systems coming out that determine if the outside air is just as cool as the inside air and will take it in to mix with the other air. But what to do if this is not the case where you are? Open a window.
The best way to open windows, cross ventilation. The main thing we learned in one of my classes, is that heat rises. If you know nothing else, you need to know heat rises. If you have the luxury of having a high window and a low window across the room, or house, open the high on one side and the low on the other. The air will rise out the top and cool air will be pulled in. Another great way to do this is if you have a basement, open those windows, and the air will rise up if the windows upstairs are open. What is great about this is that the earth is a cooler temperature and will allow the air to cool even if it is hot outside.
I like to try this all the time, in fact as I sit in my dark room at 9:30 at night, my window is still open, hoping to cool the room enough so that the night will not be hot enough to have to use any of the energy sucking programs set in play.