It is easy for me, here in breezy upstate NY, to propose that people cut back on their air conditioning, of course. We don't have it - we have maybe a half dozen days above 90 degrees every year, and even during hot periods, it only rarely stays over 70 at night. When people mention that they've had a two weeks over 100, with night-time lows of 80, well, again, it is easy for me to say. But remember, you can laugh at me in January when you are wearing sweaters and picking kale and the temps are -15 with 3 feet of snow here. Trust me, when the time comes, we'll be talking about heat too.
But at a minimum, now is a good time to think about ways of minimizing your use of cooling technologies. I'm sure there are plenty of you out there who are more expert than I at this by necessity, but here are some suggestions. The first is to minimize a/c use - use fans whenever possible, get good air circulation going, open windows at night to cool things off and close them during once things warm up to keep the coolth in, pull down shades to reflect light. You can consider an attic fan (they make solar models too, get wet (take a quick shower, or visit a public pool, lake or ocean, or just sit with your feet in a pan of cool water - works miracles), keep hydrated, and above all adapt. The simple fact is that we react most strongly to heat when our bodies encounter temperatures for the first time - or think they do. That is, after a day in an air conditioned office, an 85 degree evening feels unpleasantly hot, while a day spent getting accustomed, adapting and dealing with the temps might be one on which you notice a real cool down when things drop from 90 to 85.
If you are considering investing in a/c, the money might be better spent adding insulation. If you are building a house, consider thermal mass to keep things cool. Or perhaps you can spend your summers in your basement. If the problem is heat at night, the classic solution is to sleep outside - consider setting up a screen house or a tent, and spending your nights out during the worst weather. I've heard good things about the "Chillow" as well, a pillow with an interior cooling device to keep it cool. I don't think they are safe for kids, though.
You can cook outside as well - consider an outdoor oven, or even building a summer kitchen, so you can dissipate the heat into the outdoors. Solar ovens are a logical solution to avoiding heating up the house, and turning off your computer, changing over to CFLs, and unplugging a lot of your electronics will cut the ambient heat in your home from electric devices.
Those in very dry climates might well do well with a swamp cooler, but they don't work well in humid places. But many hot, wet, poor places, where a/c is an unaffordable luxury handle the issue by showering or using water. In Vietnam, "have you showered" is as frequently asked as "have you eaten" and often the "shower" is simply a bucket or a tin can with holes punched in it - but it is remarkably refreshing. The water can be retained and used for irrigation on non-food plants later.
If you do need a/c, keep it up as high as you can tolerate - 80 should be enough to keep everyone from heat stroke, and don't use it if the day is cool enough to tolerate, or when you aren't home. Or perhaps you could get away with using public a/c on the worst days - really hot days are a good time to head to the library. If you can avoid using private a/c late in the day, you may cut the risk of local brown and black outs, which tend to happen at the end of very hot work days, when businesses aren't shut down yet and people go home and flick on the a/c.
The most vulnerable people to heat stroke are very young children and the elderly. But even they can often manage without air conditioning if they have enough care and attention. For example, many elderly people simply feel cold even when it is hot - but their bodies know otherwise, and react normally. My husband's grandfather wanted to wear heavy sweaters on 90 degree days, and it really took a lot of attention to ensure that he was kept hydrated, coolly dressed and comfortable. Remember, water can substitute for a/c in many cases (and for those in dry climates, the water you use to cool your body may well be less than the demand for water created by power companies) - consider putting children in a small pool (under supervision, or helping an elderly person sit with their feet in the water or a wet bandana on the back of their necks. Make sure you visit and get to know your elderly neighbors - you could keep them alive in a heat wave.
Ultimately, there are times and places where some cooling is necessary - and in a warming world, that's likely to remain true for a while. But the irony is that as we deal with our personal comfort, we make the world more toxic and hotter for others, so we need to, as much as possible, cut back on our cooling energy use.