NEW YORK, June 24, 2025 (AFP) - A potentially life-threatening heat wave enveloped the eastern third of the United States on Monday impacting nearly 160 million people, with temperatures expected to climb to 104 degrees Fahrenheit (40 degrees Celsius) in the New York metropolitan area.

The country's first significant scorching heat of the year arrived over the weekend and peaks Monday and Tuesday in Washington, Baltimore, Philadelphia and New York City.

"This extreme heat will not just be uncomfortable and oppressive for New Yorkers," warned Mayor Eric Adams, adding that each year heat claims the lives of 500 people in this city of eight million.

"It's going to be brutal and dangerous if you do not treat it with the understanding that we want you to," he added.

As sweltering heat enveloped the city, authorities urged seniors, people with health problems and those without air conditioning to stay hydrated and seek help at designated cooling centers such as libraries and recreation facilities.

Heat records tumbled across parts of the US Northeast, including in Central Park, known as the lungs of Manhattan, where Monday's temperature of 96 degrees broke a record that had stood since 1888, according to the National Weather Service.

"Extreme Heat Warnings and Heat Advisories across much of the eastern third of the country (are) affecting nearly 160 million people" across at least 29 states, the NWS reported.

"This level of HeatRisk is known for being rare and/or long duration with little to no overnight relief, and affects anyone without effective cooling and/or adequate hydration," the agency warned.

Meteorologists are describing the intensifying weather pattern as a heat dome, a high-pressure system that traps air and leads to steadily rising thermal readings.

For many in the Big Apple, avoiding work in the searing heat was not an option.

"We have to endure it, because otherwise what are we going to survive on?" Manuel, a manual worker repairing a building facade in New York's Harlem neighborhood, told AFP.

"Sometimes we stop because it's a danger. We don't all have the same energy, but you have to endure," he added.

In the Washington Heights neighborhood, authorities opened several fire hydrants so residents could seek relief with the gushing water.

One of the local heroes was Ronald Marcelin, a 44-year-old air conditioning technician sweating profusely as he repaired a pizzeria's AC unit.

"I'm taking the heat so that everyone else can cool down," Marcelin said with a grin.

- Triple digits -
The soaring temperatures come just as New Yorkers head to the polls Tuesday for the Democratic primary that will decide the party's mayoral candidate.

It promises to be a tight race between Andrew Cuomo, who is seeking political resurrection after resigning in disgrace as state governor in 2021, and rising left-wing star Zohran Mamdani.

Over the weekend, Cuomo urged residents to cast their votes even if the temperatures hit 100 degrees Fahrenheit.

In Washington, the heat index -- what the temperature feels like with humidity factored in -- was forecast to soar to as high as 110 F on Monday, and the mayor's office urged residents to take advantage of cooling centers.

Scientists say extreme heat waves are a clear sign of global warming, and they are expected to become more frequent, longer, and more intense.

Fueled by human-caused climate change, 2024 was the warmest year on record globally -- and 2025 is projected to rank among the top three.