Those suffering with an unusual hot spell that perhaps doesn't justify a permanent install of a normal air conditioner should not overlook the potential of the "evaporative cooler" if the relative humidity isn't extremely high.

Friends and relatives in norther Texas still have used them quite recently, and with proper shading of windows and minor control of "venting" to hot air outside a temperature drop of 15 or 20 F (8 - 10 C) can be achieved pretty easily.

All that's required is "something wet" that you can blow air through, across, or around with a fan. Most of the "installed" ones hooked up to a water line, but you can replenish a tank or bowl periodically to make that optional. To keep the medium wet, you'll need a small pump to recirculate water, even if you tap onto a faucet, since it won't all evaporate in a single pass. Small aquarium or "waterfall" pumps are plentiful in my area fairly cheaply and should work quite well.

They do raise the humidity, but usually not enough to offset the cooling provided. The higher humidity might make them "not useful" for the library, but for living spaces in a home they may work quite well, especially for a "limited use" method.

For outdoor use, small "misters" have been popular here, although they do tend to muddy the areas where used. The ones common in the garden shops here attach to a garden hose, and the water doesn't recycle, so it accumulates somewhat. Used with a small pool they can create a nice "cool spot" for relaxing if one happens to see them easily available.

When under "heat stress" it's usually a good idea to cut back a little on the coffee, perhaps the tea, and in extremes even the alcohol¹, as they all have diuretic effects. Of course the cup'a can be countered by adding to the intake of clear liquids up to a point.

¹ Reducing the alcohol probably is the most effective, but is perhaps an extreme measure, even for the benefit obtained, for some.

John