"Though it'll be a touch cooler, we'll be trading heat for humidity, so it will still feel pretty hot," said Jim Hayes, meteorologist for the National Weather Service in Mount Holly.
With Wednesday's forecast calling for a second day of temperatures over 100, the Philadelphia School District announced it would dismiss classes early.
Classes for students in the district's summer school program and the city's summer camps will be sent home at 12:30 p.m., said spokesman Fernando Gallard.
The Philadelphia Corporation for Aging activated its Heatline, a telephone service for callers to talk to nurses about medical problems related to the heat. It was last activated June 24 through 26, when four people died of heat-related causes.
The staff, with Spanish and Russian speakers, will be available from 8:30 a.m. to 8 p.m. Wednesday at 215-765-9040.
Heatline supervisor Heidi Gambino suggested that people check on elderly neighbors.
"Sometimes they don't even realize they're hot," she said.
In West Philadelphia, a neighbor went to check on 92-year-old Euretha Knotts and found her dead on the second floor of her home Monday, said Jeff Moran, spokesman for the Medical Examiner's Office.
Though windows were open and a fan was operating on the first floor, only one window was open about four inches on the second floor where she was found.
Knotts, who lived alone, was the fifth person to die from heat-related causes in the city this year.
For SEPTA and New Jersey Transit, Tuesday's extreme heat was not enough to buckle the rails, but it caused overhead catenary wires to sag. The drooping wires caused delays of up to 45 minutes on evening rush-hour trains. Amtrak took extra precautions, putting technicians aboard trains and storing rescue locomotives every 30 to 50 miles in case of problems.
Throughout the region Tuesday, people did their best to cope.
It was 98 degrees in the shade with temperatures still climbing as King of Prussia mail carrier Rich Farra lumbered slowly up Country Lane, a 40-pound bag of mail on one shoulder and a bottle of Deer Park water in his hand.
He was drenched, and the tired green towel draped around his neck had done all it could, though Farra was just three hours into his 61/2 -mile route.
Farra, 32, has been ferrying mail for a decade, but Tuesday would sear itself into his memory.
"This has got to be one of the worst hot days ever," said Farra, who lives in King of Prussia and has 500 deliveries on his route. "You really can't breathe, there's no circulation."
At 12:30 p.m., he had already been offered 10 bottles of water by solicitous clients, though he'd only downed five of them.
He weighs 230 pounds when he starts his shift, he says, but by the end of the day, he's down 8 pounds.
That's almost a gallon of water.
"Today being a day after the holiday," said Farra, "there's a lot of mail."
Dr. Michael Goodyear, chairman of emergency medicine at Riddle Memorial Hospital in Delaware County, said emergency-room visits Tuesday were about 20 percent higher, bumped up by older patients with heat-related problems and heat-aggravated ailments.
"Every other disease gets a little worse on a day like this."
He said some older folks were slower to "perceive" the heat, a nice way of saying that sometimes they don't realize it is hot until it is too late.
Another problem is "they don't want to put air-conditioners on," Goodyear said, adding that some are on fixed incomes and don't want to spend the money, and others view relying on air-conditioning as a sign of weakness.
Peco Energy Co. and Public Service Electric & Gas Co. labored mightily Tuesday to crank out enough juice to feed those air-conditioners. They reported few outages.
In South Jersey, the air-conditioning sputtered at ManorCare Health Services in West Deptford and forced 146 residents to be relocated.
Horses that pull tourist carriages through Old City were given the day off Tuesday. City regulations require that the animals be stabled when the mercury rises above 91.
At the 76 Carriage Co. stables in Northern Liberties, a pair of horses walked through a set of sprinklers in a turnout yard while another was hosed down in front of a garage.
"I was just out playing with one under a sprinkler," said Eleanor Forstater, office assistant and carriage driver. "I'm soaking wet."
To keep cool, the 21 horses stabled near Third Street and Girard Avenue were given more hay in their feed mix as industrial fans kept the air moving through their barn.
"We put electrolytes in their water; it creates a Gatorade for horses," Forstater said. "We're also setting up a misting system so when they're in their stalls they'll be more comfortable," Forstater said.
On the south side of Independence Hall, Doug Thomas, playing Major Samuel Nicholas, stood in the wool uniform of a Continental soldier working hard to recruit young tourists to fight against the British.
Thomas said the heat did not bother him, but he worried about his audience. On Monday, he witnessed a little girl faint.
David Taylor, 60, dressed in a heavy cotton uniform and tricorn hat as Capt. Gideon Olmstead, said he if he was not working he would be out on his boat or at home with his air-conditioner.
"We're all still smiling and persevering," Taylor said. "It's hot no matter what you're wearing."
Contact staff writer Sam Wood at 215-854-2796 or firstname.lastname@example.org.
Inquirer staff writers Trish Wilson, Anthony R. Wood, Mari Schaefer, Vanessa Martinez, Elisa Lala, and Nicole Lockley contributed to this article.