(Repeats 1847 GMT story with no change to text)
July 27 (Reuters) - PJM Interconnection, the biggest U.S. electric grid operator, issued a level one emergency alert for Thursday as people crank up air conditioners to stave off the heat wave.
The operator issued an Energy Emergency Alert Level 1 late on Wednesday for Thursday, signaling that it had available resources to meet firm load and reserve commitments.
PJM oversees supply in a 13-state region, managing and paying on-call generators to keep power systems running.
Demand is forecast to peak at 149,060 megawatts (MW) on Thursday and 155,935 MW on Friday. This compares with a record high of 165,563 MW hit in the summer of 2006.
Meteorologists at AccuWeather expect temperature to hit 95 degrees Fahrenheit (35 Celsius) in Philadelphia and 86 F in Chicago, the two biggest cities PJM oversees.
As a heat wave bakes parts of the country, the Texas power grid hit a record high on July 18, but has so far avoided rolling blackouts, while Arizona also saw power use soaring to an all-time high last week. (Reporting by Seher Dareen and Anushree Mukherjee in Bengaluru; Editing by Kim Coghill and Mark Porter)