LAS VEGAS — Las Vegas baked Wednesday in its record fifth consecutive day of temperatures sizzling at 46.1 Celsius or greater amid a lengthening hot spell that is expected to broil much of the U.S. into the weekend.

The temperature climbed to 46.1 shortly after 1 p.m. at Harry Reid International Airport, breaking the old mark of four consecutive days set in July 2005. And the record could be extended, or even doubled, by the weekend.

Even by desert standards, the prolonged baking that Nevada’s largest city is experiencing is nearly unprecedented, with forecasters calling it “the most extreme heat wave” since the National Weather Service began keeping records in Las Vegas in 1937.

Already the city has broken 16 heat records since June 1, well before the official start of summer, “and we’re not even halfway through July yet,” meteorologist Morgan Stessman said Wednesday. That includes an all-time high of 48.8 C set on Sunday, which beat the previous 47.2 C record.

Alyse Sobosan said this July has felt the hottest in the 15 years she has lived in Las Vegas. She said she doesn’t step outside during the day if she can help it.

“It’s oppressively hot,” she said. “It’s like you can’t really live your life.”

It’s also dangerously hot, health officials have emphasized. There have been at least nine heat-related deaths this year in Clark County, which encompasses Las Vegas, according to the county coroner’s office. Officials say the toll is likely higher.

“Even people of average age who are seemingly healthy can suffer heat illness when it’s so hot it’s hard for your body to cool down,” said Alexis Brignola, an epidemiologist at the Southern Nevada Health District.

For homeless residents and others without access to safe environments, officials have set up emergency cooling centers at community centers across southern Nevada.

The Las Vegas area has been under an excessive heat warning on three separate occasions this summer, totaling about 12 days of dangerous heat with little relief even after the sun goes down, Stessman said.

Keith Bailey and Lee Doss met early Wednesday morning at a Las Vegas park to beat the heat and exercise their dogs, Breakie, Ollie and Stanley.

“If I don’t get out by 8:30 in the morning, then it’s not going to happen that day,” Bailey said, wearing a sunhat while the dogs played in the grass.

More than 142 million people around the U.S. were under heat alerts Wednesday, especially in Western states, where dozens of locations tied or broke heat records over the weekend and are expected to keep doing so all week.

Oregon has seen record daily high temperatures, with Portland reaching 39.4 C and Salem and Eugene hitting 40.5 C on Tuesday. The number of potentially heat-related deaths in Oregon has risen to 10, according to the state medical examiner’s office. The latest two deaths involved a 54-year-old man in Jackson County and a 27-year-old man in Klamath County.

On the other side of the nation, the National Weather Service warned of major-to-extreme heat risk over portions of the East Coast.

An excessive heat warning remained in place Wednesday for the Philadelphia area, northern Delaware and nearly all of New Jersey. Temperatures were around 32.2 C for most of the region, and forecasters warned the heat index could soar as high as 42.2 C. The warning was due to expire at 8 p.m. Wednesday, though forecasters said there may be a need to extend it.

The heat was blamed for a motorcyclist’s death over the weekend in Death Valley National Park. At Death Valley on Tuesday, tourists queued for photos in front of a giant thermometer that was reading 48.9 C.

Simon Pell and Lisa Gregory from London left their air-conditioned RV to experience a midday blast of heat that would be unthinkable back home.

“I wanted to experience what it would feel like,” Pell said. “It’s an incredible experience.”

At the Grand Canyon, the National Park Service was investigating the third hiker death in recent weeks. Temperatures on parts of some trails can reach 49 C in the shade.

An excessive heat warning continued Wednesday in many parts of southern and central Arizona. Forecasters said the high in Phoenix was expected to reach 45.5 C after it hit 46.6 C Tuesday, tying the previous record for the date set in 1958.

Authorities were investigating the death of a 2-year-old who was left alone in a hot vehicle Tuesday afternoon in Marana, near Tucson, police said. At Lake Havasu, a 4-month-old died from heat-related complications Friday, the Mohave County Sheriff’s Department said.

The U.S. heat wave came as the global temperature in June was a record warm for the 13th straight month and marked the 12th straight month that the world was 1.5 degrees Celsius  warmer than pre-industrial times, the European climate service Copernicus said. Most of this heat, trapped by human-caused climate change, is from long-term warming from greenhouse gases emitted by the burning of coal, oil and natural gas, scientists say.

Firefighters in Henderson, Nevada, last week became the first in the region to deploy what city spokesperson Madeleine Skains called “polar pods,” devices filled with water and ice to cool a person exhibiting symptoms of heat stroke or a related medical emergency.

Extreme heat in the West has also dried out vegetation that fuels wildfires.

A blaze burning in northern Oregon, about 178 kilometers east of Portland, blew up to 28 square kilometers by Wednesday afternoon due to hot temperatures, gusty wind and low humidity, according to the Oregon State Fire Marshal. The Larch Creek Fire closed Highway 197 and forced evacuations for remote homes.

In California, firefighters were battling least 19 wildfires Wednesday, including a 117-square-kilometer blaze that prompted evacuation orders for about 200 homes in the mountains of Santa Barbara County.
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