Rolling brownouts may also be a measure taken by the city or ComEd during extreme heat. Sometimes when it is too hot, power companies schedule power shut downs in non-overlapping sections of the Chicago area for short periods of time.
Rolling brownouts prevent system-wide blackouts in situations where the company may not be able to produce enough power to support the number of air-conditioners and fans being used during a heat wave.
Contact your local government offices or power company or visit their website to find out if rolling brown outs will be scheduled during this stretch of heat.
Should a rolling brownout or blackout occur, these are some precautions you might consider taking:
Protect your computer by using an uninterruptible power supply. These last for a short period of time after a power outage occurs. That way, you can save your work and make sure not to lose any of your files.