From the Pacific north-west to the southern Great Plains and on to the heavily populated Interstate 95 corridor, more than 85 million Americans were on Sunday under excessive heat warnings or heat advisories issued by the National Weather Service (NWS).
The agency warned of “extremely oppressive” conditions from Washington to Boston.
Even in Promised Land State Park, 1,800ft up in Pennsylvania’s Pocono mountains, temperatures were forecast to soar above 90F (32C). But with shade from the forests, cool lake water and mountain breezes, it was more than tolerable, visitors said.
Rosa Chavez, 47, a high school teacher in Manhattan, applied sunscreen at a beach on Promised Land Lake. She and her friend Arlene Rodriguez had just experienced Europe’s own heatwave while vacationing last week in Italy.
“The heat is following us,” said Rodriguez, 47, a real estate agent and property manager.
Numerous record highs were expected to be tied or broken in the US north east, the NWS said.
Philadelphia was forecast to hit 100F (38C) on Sunday before even factoring in humidity. Newark, New Jersey saw its fifth consecutive day of 100F or higher, the longest such streak since records began in 1931. Boston also hit 100F, surpassing the previous daily record high of 98F set in 1933.
At least one heat-related death, in New York, was reported. Around the region, athletic events were shortened or postponed.
Philadelphia officials extended a heat emergency through Sunday, sending workers to check on homeless people and other vulnerable residents. The city opened cooling centers and stationed air-conditioned buses at four intersections.
Forecasters urged people to wear light clothing, drink lots of water, limit time outside and check on elderly people and pets.
The mayor of Boston, Michelle Wu, declared a heat emergency through Monday and kept a dozen cooling centers open.
Organizers of the New York City Triathlon shortened the distances athletes had to run and bike. The Boston Triathlon was put off until 20-21 August.
On the west coast, forecasters warned of extreme heat until next weekend. Temperatures could break daily records in Seattle, Portland and northern California by Tuesday and be the highest since a heatwave last year killed hundreds.
Many homes in the often-rainy region lack air conditioning and authorities cautioned that indoor heat is likely to build, increasing the risk of heat-related illnesses.
Chavez, in Promised Land, said she has asthma and needs to keep her inhaler around, especially “when the heat is so thick I can’t breathe”. The breezes and clearer air in the mountains help, she said.
The heat was withering less than an hour away, at lower elevations. In Scranton, Pennsylvania, Sunday’s high was expected to be 97F (36C), and not below 70F (21C) at night.
“That also leads to the danger. People aren’t getting that relief overnight,” said NWS forecaster Lily Chapman. “That stress on the body is kind of cumulative over time.” The area also has been drier than usual, she said.