For those of us who don’t have air conditioners in our houses (or for those who do, and who wish to save some electricity), there is a simple trick called a “whole house fan.”
The bigger ones can be professionally installed, but a small unit is very easy to make. Just find your attic trap door and cut a new piece of plywood the same size as the trap door. Then cut a hole in the plywood slightly smaller than a household fan.
Pop the fan into the hole, so that it forces air into the attic. Then, in the late evening, when outside temperatures are lower than in the house, crack open a few windows and turn the fan on.
Leave it on overnight and it will draw cool air into the house. Then, in the morning, turn it off, shut the windows and draw the drapes. We’ve been doing this for years, and it’s always nice to come home to a house that is five to 10 degrees cooler than the outside oven.