There is a bigger problem at hand than high utility bills: on the hottest days of summer, electric system usage during peak hours can result in an overloaded generation system or delivery grid... and that can mean brownouts- or even worse- blackouts.
Another interesting challenge that hot weather and its close cousin water shortage poses is that nuclear power plants actually have to reduce their power output during heat waves, or shutdown completely because of lack of cool water. Nuclear reactors use fission to heat water into steam, turning turbines that generate electricity, and then cool that steam back into water and feed it back through the core, repeating the process. Without lots and LOTS of water this system doesn't work. One reactor pumps 1 BILLION gallons a day of water through its cooling systems and back into waterways, other reactors (the type with the distinctive cooling stacks we all know from the Simpsons) can evaporate 17 million gallons a day into the air! Without adequate water supplies, reactors must drop energy output or shutdown.
Illinois is a large user of nuclear power, but is at a lower risk of being affected by this type of issue than the southern states because our rivers and lakes are cooler, but don't think that when any reactor in the country shuts down unexpectedly that everyone's electricity rates won't go up!
There are ways to avoid the cooling crunch: The easiest way to combat an overloaded grid, while still enjoying the same habits and lifestyle, is an air conditioner cycling system like ComEd's Nature First program. Depending on the program you select, ComEd will credit your bill either $5 or $10 dollars a month for 4 months (from the beginning of June, till the end of September) if you let them attach a small radio controlled switch to your central air conditioning unit's outside compressor. If and when demand cannot be met, or the grid is approaching a danger threshold, ComEd sends a radio signal that will turn off the AC compressor, but still allow your homes air circulation fans to run. The $5 a month credit will allow ComEd to cycle your compressor on and off every 15 minutes, while the $10 credit will allow for one continuous 3 hour block of time where the compressor is disabled. This program is only active during weekdays, and having been a user of the system for some years myself, I have never experienced more than 4 activations of the service in one year, and they tend to happen in the mid afternoon, when I'm not home anyways. The fact that most AC systems are oversized for the house they cool is another story, but running your air on and off for 5 minutes at a time is really horrible for efficiency!
For the more flexible users of electricity, Illinois along with ComEd have pioneered a new and innovative program for residential users known as 'Residential Real Time Pricing' or RRTP. Under this program, you pay the hourly market rate for electricity, rather than the 'averaged' market rate. You can get a hint of the difference in how these these rates fluctuate by looking at ComEd's current residential 'Basic Electric Service' (or BES) rate sheet, where 'general lighting' costs 7.212 cents/kWh while 'dusk to dawn lighting' costs only 2.760 cents/kWh.
If you are thinking "so what, that's not that much difference", consider that I have saved more than $800 over the 5 years I have been on a Real-Time Pricing program, by simply thinking about how and when I use electricity, and making some small adjustments to my life!
I was an early user of this program when it was still administered by the community energy cooperative, and it was known as the Energy Smart Pricing Plan, or ESPP. ESPP was wonderful because you knew what electricity rates were going to be for the day the evening before, and could plan your activities accordingly if rates were to be high. ComEd's current RRTP program uses a rate known as BES-H (residential-hourly), this pricing plan gives you an estimate of tomorrows prices, but you will only know what you are paying for that power as they day progresses; and sometimes what you end up paying is way off the estimated cost.. These prices change every 5 minutes, so good luck keeping up with them! Luckily, there is a service available for ComEd customers on the RRTP program, called Load Guard (open PDF). Load Guard lets you use the same AC compressor switch installed when enrolled in Nature First, and takes the concept a step further: if your electricity rates exceed a preset threshold of either 10 or 14 cents/kWh, your AC compressor is cycled on and off just like in the Nature First $5/ month program.
There are many ways to beat the heat, of course turning off the AC and sipping some iced tea in frot of a fan is a great way to lower your electricity consumption, but few homeowners are willing to give up the luxury of Air Conditioning. So if you have central AC and love it, why not save 20$ or 40$ a year by signing up for Nature First
(EDIT: The Nature First program has been renamed "Central AC Cycling" by ComEd, the link is now updated to take you to the new website).