Back in the olden days, people had some remarkably simple way to deal with the heat of summer.
They would sweat. Among the lower classes, they would take off their shirts, and pants, and sit around in their underwear. Of course those of the more genteel classes could not avail themselves of these solutions, and they suffered greatly.
Tris
In New England enclosed front porches were common, usually with trees right outside. They had shadows, widows to provide a cross breeze, along with screens to keep the vermin out.
Animals sweat. Men perspire. Women glow.
My apartment in a vintage 1910 apartment building has some of the features described - high ceilings, a shotgun hallway that runs from the door straight back to a window in the living room, and transoms. But the transoms have been sealed for security reasons, and leaving the front door wide open isn’t a great option these days. So, perched on the top floor as I am with a lone a/c woefully inadequate to the task, the only real option for staying cool is taking a cold shower and then sitting in front of a fan in my underwear.
I didn’t think to mention sleeping porches - people would sleep on the screened in porch when it got really hot. Especially the kids. I have an enclosed laundry room that was obviously made out of a sleeping porch - in the back, under the shade of the pecan trees, etc.
Yes. I was born and partly raised (In PA) in an old house with a big front porch with chairs and most importantly a swing. There were two families living there (Mum’s and Dad’s) and us kids. We’d all gather there in the hot summer evenings and while us kids played (Chasing lightning bugs) the adults would talk and drink iced tea. (Kool-Aid for the kids) 
The brick house I grew up in had a cupola when it was built in the 1870s, but it was removed before we moved in. The idea was that warm air would rise out through the cupola’s windows allowing cooler air to flow in through the first- and second-floor windows. I’ve read that prairie dog dens are ventilated on the same principle.
My great-grandfather solved the problem by having two houses about a mile apart. The summer house was by the river, open to the breeze, well shaded, uninsulated, with lots of windows, and had a separate kitchen. As a dairy farmer, he wasn’t rich, but he was pretty well off by the standards of the other neighborhood dairy farmers.
It was also common in the Old South for “ladies” to “retire” during the afternoon; i.e. 1 to 4 pm when the day would be at its hottest. Remember the party at the beginning of “Gone With The Wind”? Kitchens would sometimes in a separate building to keep the heat out, along with the smell of cooking food.
These seem to be popular in Germany, at least in Baden-Baden/Heidelberg areas.
My grandmother’s house had an enormous front porch that stretched all the way across the front of the house. The thing was completely screened and had a variety of porch swings and other things a kid could sleep on. There were also large trees scattered around. This was in Kentucky so it usually wasn’t all that hot until July-August times.
Testy
I live in a house that was built around 1914, in an area where summer temperatures regularly hover around 100 degrees. I suspect the house is designed so that, with all the doors and windows open (upstairs and down), you’d get a nice chimney effect. Combined with some nice shade trees, that would keep the house relatively cool.
Problem now is this: we’ve got a massive fir tree in front, on the east side of the house, but no effective shade trees on the south and west sides, which are the sides the sun beats mercilessly upon during the day. And nowadays, in this neighborhood, leaving the doors open at night just isn’t an option, so AC is a must.
I don’t know why there are no shade trees on the hot sides of the house, but I suspect it has to do with neighboring construction. The house to the south and the apartments to the west are clearly several decades newer than this house. I imagine the trees were ripped out to make room. I’ll bet the lot to the west was originally my house’s lawn. My house sits rather prominently on a rise, and the newer house is right on the corner of two streets. I’ll bet my house was a grand, fancy structure when it was new, but it’s a run-down, ugly thing now.
I can attest to the efficiency of high ceilings, wide eaves, wrap around porches, and trees (although a previous owner cut down most of the ones shading the southern side of the house, which can really get blasted with sun). Our house, which we’ve lived in for a month now, was built in 1810. Last week it went over 90F, and it was cool and comfortable downstairs. We still don’t have any ceiling fans (they’re in the plans), and the double hung windows are mostly painted shut. It did get a little stuffy upstairs, but nothing near what we experiences in our other house (which is on the market). The other one was built in 1935 - it’s a cape cod style laid out in a spiral inside (really a unique sort of layout, hard to describe). The only comfortable room there is the kitchen because it’s at the bottom of the house in the back and gets no sun.
Old windows can be taken apart and rebuilt. I’ve seen it done. Maybe you can find a howto site with YaGoogle.
Now we know how New England widows made a living in the summer. 
What gets me is with all the heat, why the hell did people think (especially women) that layers of petticoats, corsets, and whatnot was the way to go?
Say it’s a lovely June day, and Scarlett isn’t going to a party, she is just hanging out around Tara. Her father has grounded her, so no gentlemen callers, so she’s not getting dressed to entertain. Would she will be flitting around the mansion, slapping Prissy and trying to outwit Mammy, wearing a chemise, a corset, and petticoats and pantaloons under her dress? :eek:
Deep porches are a very regrettable victim of AC. Nothing is more fun than a deep, wraparound porch with a bunch of chairs, swings, etc. Often results in a drier basement as well.
Also, never underestimate the power of acclimatization, either. If your workplace is 72 degrees all year and you have good air-conditioning in your car, 90 at home is really hot, and stays hot all summer. If there is no air-conditioning anywhere, it becomes more tolerable. It’s not a perfect system, of course, but I have spent an Alabama summer with no air-conditioning at all, and I know that bothered me much, much less than times when I just didn’t have air-conditioning at home.
Yeah, I’ve seen it done on This Old House, but it would be difficult, expensive, there’d probably be some breakage, and when I was done I’d still be left with single pane ancient windows.
Women were encouraged to wear their corsets all the time, the better to keep a 16" waist. Over it they wore a chemise and a robe–still too much clothing. In hot weather all I wear at home is a large teeshirt and panties.
I live like that! I was excited when we moved into this 1890s building that still has the original interior shutters in the bedroom. The windows are floor-to-ceiling, and there’s a top and bottom section of shutters. I’ve been surprised by what a difference it makes, both in cooling the room in the summer, and holding heat in the winter. I have a whole summer and winter system worked out.
I can attest to that. When I was first in Vietnam, the heat was oppressive and I couldn’t function for at least a month. Then we once had an occasion where we had to stay outside in the open air all night, and we were all bundled in blankets to keep warm and passing around “coffee” in a thermos (really wine) to help. Then someone said, shivering, “I wonder how cold it really is,” and we got a thermometer. It said 72F. We were so acclimated that it felt cold.
No wonder they fainted and had to carry smelling salts. I wonder if any of them past the pre-teen years knew what a great big deep breath was.