Redditor _Orchidia_ is dealing with a broken air conditioning system, and it will be a few days before a tech is available to repair it. She reached out for suggestions for getting through that time, and got a lot of advice from folks who don't even have air conditioning. After all, no one had central air a hundred years ago.
The house _Orchidia_ lives in has two floors. The upper floor is much hotter, so she should sleep downstairs temporarily. But the windows upstairs should be opened to take advantage of the stack effect. Warm air rises, so keeping the stairwell open and windows open on both floors should keep air flowing upward and the lower floor cooler. Any transoms should also be opened- that's what they are for. If you don't have a second floor to draw the hot air into, ceiling fans can be used to draw hot air upward toward the ceiling.
She can also arrange for greater air flow on the lower floor. Open the windows and create an air flow deigned to move air in the rooms you use the most. A fan to draw hot air out of the house is best, but for the utmost efficiency, don't put that fan directly in the window. A fan further back from the window takes advantage of Bernoulli's principle. Wolf_Science explains this visually, and shows us the best fan placement.
Another trick for keeping cool without A/C is evaporative cooling, which is simply passing air over water to produce cooler air. You can fashion a swamp cooler to do that for you. Here are ten do-it-yourself designs ranging from simple makeshift devices to deluxe models if you have the tools and skills.
Redditors also recommended _Orchidia_ buy a window air conditioner to get through the wait, or possibly stay with someone else until the HVAC tech can get there.
(Image credit: _Orchidia_)