When we first moved into the house, DH installed an attic fan and a whole house fan. The attic fan is set to turn on when the attic air reaches a certain temperature. It kicks on and then blows the hot air OUT.
At night, we open up all the windows and turn on the whole house fan. This one sounds like a jet engine, but it sucks all the cool air in from the outside, then blows all the hot air out.
It is a good idea to invest in insulated curtains or window treatments. That has helped SOOOO MUCH for our home!