East Coast still sweltering, but cold front bringing relief

NEW YORK (CNN) -- The first taste of relief from sizzling hot temperatures reached the northern Plains states Thursday, thanks to a cold front that brought showers and cooler weather.

But parts of the East are expected to have unusually warm weather into the weekend as the days-old heat wave lingers.

In Massachusetts, police in the town of Rowley were investigating whether the death of a 3-year-old girl was heat-related. The governors of New York and New Jersey ordered all state offices to close early Thursday to reduce the amount of energy they are using.

VIDEO Like most cities in the U.S., New York is trying to find ways to beat the heat this summer. CNN's Brian Palmer reports (August 9) Play video (QuickTime, Real or Windows Media)   RESOURCES High temperatures across the U.S.

The New York Independent System Operator (NYISO), which manages the state's energy supply, declared a state of emergency Wednesday when reserves dipped below the required minimum. It expects an even higher demand Thursday.

"We hope to meet the load today," said NYISO spokesman Steven Sullivan.

The region is in its fourth straight day of temperatures higher than 90 degrees, which increases demand on the system.

He credited voluntary conservation by customers and businesses with helping to handle the demand.

"We saved about 1,000 megawatts, which is no insignificant amount," said Sullivan.

The Long Island Power Authority declared a Stage One Power Alert Thursday, indicating the system was "stretched to its limits." It urged its customers to save energy and reduce their electricity use between the peak hours of 2 p.m. and 6 p.m.

Some 22,000 heat-related power outages have occurred on Long Island in the past three days, LIPA said, and it expected more such disruptions Thursday afternoon.

"State and local emergency management authorities, and local elected officials have been notified by LIPA of the potential for power outages on Long Island," the authority said.

In addition to closing government offices, New York Gov. George Pataki waived admission fees to all state parks with swimming beaches so people can cool off in the water.

Ford making fans available

Detroit, expecting a high of 96 degrees, had about 7,000 scattered power outages Thursday morning. Detroit Edison blamed high energy demand. To help workers cool down in the hot vehicle assembly plants, Ford Motor Co. was making Gatorade, ice, water and fans available, said spokeswoman Della DiPietro.

Brian Quantz, the vice president of United Auto Workers Local 900, said conditions inside the auto plants were hot and miserable, "but it ain't nothing new. Not to us."

In a turn of events, big cities in the Northeast are expected to top the high temperature Thursday in Phoenix, Arizona, a traditional hot spot. Highs of 100 degrees are forecast for New York and Philadelphia, while thunderstorms and showers are expected to keep Phoenix in the upper 90s.

"Things are a little out of phase right now," said CNN meteorologist Ross Hays. Excessive heat warnings have been issued in cities across the Northeast. "Philadelphia and cities all through New England are expecting records today," Hays said.

The heat warning did not keep visitors away from the National Zoo in Washington, where they watched pandas Mei Xiang and Tian Tian rest in a grotto kept at a nippy 55 degrees. Other animals made use of pools and misting systems to escape the heat.

"I'm much more concerned about visitors," said Lisa Stevens, senior curator at the zoo. "The animals are seeking cool places and are inactive. The visitors are out here walking around in this heat. So we really are more concerned about them and want them to be very careful about taking time to cool off." New York City opened about 400 cooling centers throughout its five boroughs to help residents, mainly the elderly, escape the heat.

Emergency heat plan in action

The centers are part of the city's "emergency heat plan" activated this week for the first time in two years, said Frank McCarton, of the Office of Emergency Management.

"We have seen an influx of heat-related EMS runs in the past several days, the influx being over 80 calls," he said.

Power companies in New Jersey and Pennsylvania reported peak demand, but few outages.

The 1.9 million customers of New Jersey's Public Service Electric & Gas consumed a record of 9,966 megawatts Wednesday, and the company expected a near-record again Thursday.

"We started out hotter this morning than yesterday, so I'm sure load demand is up," said spokeswoman Leslie Cifelli.

Peco Energy, which serves Philadelphia, recorded the second-highest demand in company history Wednesday. "The demand, we believe, will reach unprecedented levels today," said spokesman Michael Wood. "We have not yet set a peak demand record yet, but we anticipate that today." Further west, the cold front is having a significant effect on the heat in the Plains states.

Pierre, South Dakota -- which reached 104 Wednesday -- and Minneapolis, which saw a high of 94, were both expecting a high of only 80 degrees Thursday.

"The upper Plains, moving into the Great Lakes, is showing some cooling today thanks to a cold front that is moving down from Canada and bringing cooler air," said meteorologist Kevin McCarthy of the National Weather Service.

New England back to normal by Friday

By Friday evening, he said, that cool air will reach New England and return temperatures to normal levels.

"Today is probably the worst of the heat wave," said McCarthy. "People will see improvement over the weekend." Sullivan, of the NYISO, said customers can contribute major energy savings by simply closing the blinds during the day and turning the air conditioner up to 78 degrees.

He recommended using major appliances, such as dishwashers and washing machines, after 8 p.m.

The New York Office of Emergency Management advised using air conditioners in only one room at a time, and using fans whenever possible.