By SETH BORENSTEIN

NEW YORK (AP) — Extensive triple digit heat, broken temperature records and oppressive humidity piled up into a steaming mess as the heat dome crushing the Eastern half of the nation sizzled to what should be its worst Tuesday.

New York City’s John F. Kennedy Airport hit 100 degrees Fahrenheit a little after noon, the first time since 2013. Then Baltimore, Philadelphia and Boston joined the 100 club. More than 150 million people woke up to heat warnings and forecasters at the National Weather Service expected dozens of places to tie or set new daily high temperature records Tuesday. The dangerous heat sent people to the hospital, delayed Amtrak trains and caused utilities to urge customers to conserve power.

“Every East Coast state today from Maine to Florida has a chance of 100 degree actual temperature,” said private meteorologist Ryan Maue, a former National Oceanic and Atmospheric Administration chief scientist.

Fryeburg, Maine, also hit 100, for the first time since 2011.

“Getting Maine to 100 degrees is infrequent,” Maue said.

Tuesday’s heat came on top of 39 new or tied heat records Monday. But just as dangerous as triple digit heat is the lack of cooling at night, driven by the humidity.

“You get the combination of the extreme heat and humidity but no relief,” said Jacob Asherman, a meteorologist at NOAA’s Weather Prediction Center. “It’s kind of been just everything stacked on top of itself…. It just speaks to how strong this heat wave is. This is a pretty, pretty extreme event.”

Asherman and Maue said Tuesday is the peak of the high pressure system that sits on top of the Mid-Atlantic and keeps the heat and humidity turned up several notches.

“Nobody is immune to the heat,” said Kimberly McMahon, the weather service public services program manager who specializes in heat and health.

Heat turns dangerous

Dozens attending outdoor high school graduation ceremonies in a northern New Jersey city on Monday were treated for heat exhaustion and related problems, including 16 taken to hospitals. The Paterson school district held ceremonies in the morning and the afternoon as temperatures soared to nearly 100 degrees. Officials halted the second ceremony about an hour after it had started due to the heat.

And in New Hampshire, two 16-year-old hikers were rescued from a mountain in Jaffrey late Monday afternoon, overcome by the heat, the New Hampshire Fish and Game Department said. They were described as being in and out of consciousness and taken to a hospital.

The heat hit New York City as residents headed to the polls for the city’s primary election. In Queens, Rekha Malhotra was handing out flyers in support of Democratic mayoral candidate Zohran Mamdani while wearing a pink electric fan around their neck.

“It’s 90 bazillian degrees and here I am,” said Malhotra. “I could have been phone banking.”

“I have all the things — hat, ice and this,” Malhotra added, clutching a commercial-grade spray bottle.

Utilities across the Midwest and East braced for the surge of extra demand in the heat, at times asking people to cut back on air conditioning when it felt like it was needed the most. In Memphis, Tennessee, residents were asked to turn off unnecessary lights and electronics, wait until nighttime to use dishwashers, washing machines dryers, and raise thermostats a few degrees, if health allows.

No relief at night

The heat and humidity during the day was compounded by humid nights where the temperatures don’t drop much and the human body and the electric bill don’t get a break to recover, said Bernadette Woods Placky, chief meteorologist at Climate Central.

“The longer the heat lasts, the more it wears on the body, the more it wears on the health,” Woods Placky said.

A good rule of thumb is the temperature has to get at least as low as 75 degrees, if not lower, for people to recover, McMahon said. That’s a lesson from the Pacific Northwest heat wave of 2021, when many of the deaths were older people who lived at home and died at night because it wasn’t getting cool enough, she said.

“Unlike other weather hazards, heat does have that compounding effect on the human body. Your body tolerates less and less heat as the days go on,” McMahon said.

Because warmer air from human-caused climate change holds more moisture, making it more humid, summer nights are actually heating up faster than summer days, Woods Placky said. That’s why the Dust Bowl of the 1930s hit high temperatures similar to now, but it wasn’t as warm overall because the nights cooled, she said.

The United States daytime summer high temperature has increased 2.2 degrees Fahrenheit since 1975, but the nighttime lowest temperature is now on average 2.6 degrees higher, according to NOAA data. In Baltimore, summer nights have warmed 4.5 degrees Fahrenheit since 1975, while summer days only 1.5 degrees, the data showed.

Marc Savenor, who owns Acme Ice and Dry Ice Company in Cambridge, Massachusetts, struggled to keep up with phones ringing as the heat wave overwhelmed ice machines and refrigerators, forcing customers to seek emergency supplies.

“During the heat waves, my phone will ring at 3 in the morning till 11 at night,” Savenor said as workers shoveled dry ice into pellets. “There’s no help for the weary here, because you’ve got to get it when it’s coming in and everybody wants some.”

Air conditioners and fans have been flying off the shelves at Khan Electronics in Queens, owner Mudassar Khan said.

“It started getting hot at night. People buy air conditioners when they feel uncomfortable at night,” Khan said.

“Relief is coming,” Maue said, predicting that on Friday, New York City probably won’t even get into the 70s. “It’ll feel incredible.”

Associated Press writers Cedar Attanasio in New York; Bruce Shipkowski in Trenton, New Jersey; Adrian Sainz in Memphis, Tennessee; Rodrigue Ngowi in Boston; and Patrick Whittle in Portland, Maine, contributed.

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