Midwest, East Coast Baking

Much of the country is blistering as a heat wave that has brought record-breaking temperatures to the Midwest and Northeast shows no sign of letting up in some parts until Friday.

The sweltering conditions knocked out power, depriving thousands of the air conditioning, electric fans, and ice cubes necessary to keep cool.

For millions more, the boiling heat and stifling humidity have added up to pure misery. While the Plains states might see some relief on Thursday, it is expected to take at least another day for some parts of the East to start cooling down, forecasters say.

From the East Coast to the Great Plains, temperatures inched into the upper 90s and the humidity made it feel more like 100 in some places.

In Atlantic City, N.J., the temperature was 98 degrees at midday, but the heat index — how hot your skin feels — was 108 degrees. In the nation's capital, temperatures hit 96 degrees, but the humidity made it feel like 106 degrees. New York's Central Park hit 97 degrees by early afternoon, but it felt like 100 degrees.

Today brought little relief for many who suffered through similar swampy conditions on Tuesday: Bismarck, N.D., was typical, reaching a high of 96 degrees, but with the humidity it felt like 113.

Check temperatures in your area at weather.com.

It got so hot in Minnesota that farmer Mike Peterson had to hose down his pigs. "On a day like this, they're just under more stress," he said.

Zoo officials in Binghamton, N.Y. were looking out for their own animals today, closing the city zoo early as the heat index soared.

Raising Heat Awareness

In Wisconsin, several Green Bay Packers football players overheated while training on Tuesday and had to be treated with ice towels and water. And in Newark, N.J., where the heat index reached 106 degrees, six firefighters suffered heat exhaustion while fighting a house fire.

The death of Minnesota Vikings lineman Korey Stringer from complications of heatstroke last week has raised awareness of the dangers of strenuous exercise in the heat. According to the National Weather Service, heat is the No. 1 weather-related killer in the country.

In this kind of heat, sitting in a hot car can be just as perilous. On Tuesday, a man died of hyperthermia in Oak Park, Mich., after being found inside a locked car.

In Wisconsin, officials say heat has played a role in 10 deaths in the past three weeks. Heat also was blamed for the deaths of a man working on a roof Monday in Madison County, Ky., and that of a 76-year-old man in West Chester, Pa., who had no air conditioning.

In cities nationwide, officials urged people to check on elderly residents, especially those who may not own air conditioners.

Utilities Feel the Heat, Too

The heat wave has electric companies nationwide bracing for high power demand and urging people to conserve energy.

Blackouts plagued residents in New Jersey and in Minnesota. About 12,000 customers lost power Tuesday in New Jersey but service was restored during the night. About 2,400 Xcell Energy customers in Minnesota had no power early today for a third day.

In Raleigh, N.C., power was knocked out temporarily to 20,000 homes as an energy substation exploded in a huge fireball for as yet undetermined reasons. Every police unit in the city responded to the scene, and 30 traffic accidents were blamed on the mess.

As Boston declared its first heat emergency, many utilities in New England expected to set power consumption records this week, especially as forecasters are not anticipating any break in the infernal conditions until the weekend.

According to New York's Independent System Operator, electricity usage hit an all-time high.

"There's a little bit of extra juice floating around out there, some from our neighbors to the north [Canada]. But, boy, it's tight," New York ISO spokesman Steve Sullivan told The Associated Press.

New York's Office of Emergency Management opened 400 "cooling centers" — air conditioned senior centers, schools and other public facilities. They were never opened last year. Emergency management officials also kept the city's pools open an hour later. Massachusetts also planned to keep many state-run pools and beaches open late to combat the heat.

In Nebraska, which has been without measurable rainfall since July 3 and has had 11 days of 90-degree heat in that time, authorities are not only worried about the increased power consumption that comes with a heat wave. They're fretting over the rapidly dropping water supply.

"The heat has stressed our water supply system. Our customers, because of watering of lawns, have increased their use of water significantly," said Gerald Radek, general manager of Omaha's Metropolitan Utilities District. "We've asked our customers to voluntarily cut back on their water use by going to alternate-day watering, and they've been very cooperative in that." ABCNEWS' Dan Harris contributed to this report.