QUOTE: "Utilities say they're ready for high power demand and widespread electricity shortages or outages are unlikely. Lines and equipment are not fully taxed and there is more generating and transmission capacity available than usual because of the weak economy. Also, not many major storms are in the forecast, meaning fewer downed power lines."
You can see there are a few positive notes there so hopefully the grid won't get completely overwhelmed, but think of all the air conditioners running full speed and you can imagine the potential strain.
QUOTE #2: "The heat wave began a week ago in the Plains states and is expected to spread east through the weekend. It is lasting longer than most heat waves and is spread over an unusually wide area, according to Travis Hartman, the Energy Weather Manager at MDA Earthstat, which proves forecasts for utilities and other weather-dependent businesses."
Looks like it will still be hanging around for a while, so if you are in one of the affected regions be safe and wise. This is one of the emergencies you prepare for.