Update, July 2017: After two summers of experimenting, I am a firm believer in closing windows and blinds to keep the house cool when it is hot outside. But many people will resist. They can’t tolerate closed windows and blinds when it’s a beautiful sunny day. There’s evidence of this when I’m riding the bus. The bus is air conditioned, but people insist on opening the windows, which actually makes the bus warmer. But I admit that there’s some pleasure in experiencing a breeze on a sunny day, even if that breeze is warm.
The original post: The assumption here is that you want to keep your house as cool as possible in hot weather without resorting to air conditioning. I checked* a couple of dozen Internet entries for stances on whether windows should be open or closed to achieve a cooler house when the weather is hot. There were many entries to pick from; lots of people have reflected on this. The consensus is, it depends.
Generally, if your house is decently insulated, keep the windows and blinds closed when the sun is shining. Open the windows in the evening and at night. More specifically, keep the windows closed when the outside temperature is hotter than it is inside, and open the windows when it’s cooler outside than inside.This doesn’t work if your house is not well insulated and was illustrated for me at a house in my past. We had a stand-alone garage that wasn’t insulated, and it got quite hot in there in the summer if the doors and window were closed. Our adjacent house didn’t get nearly as hot.