LAS VEGAS — Las Vegas baked Wednesday in a record fifth consecutive day of temperatures sizzling at 115 degrees Fahrenheit or greater amid a lengthening hot spell that is expected to broil much of the U.S. into the weekend, the National Weather Service said.

The temperature climbed to 115 at 1:13 p.m. at Harry Reid International Airport, breaking the old mark of four consecutive days. On Sunday, the heat wave set Las Vegas’ all-time temperature record of 120.

Even by desert standards, the prolonged baking that Nevada’s largest city is experiencing is nearly unprecedented.

“This is the most extreme heat wave in the history of record-keeping in Las Vegas since 1937,” said meteorologist John Adair, a veteran of three decades at the National Weather Service office in southern Nevada.

Keith Bailey and Lee Doss met early Wednesday morning at 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.

Alyse Sobosan said this July has been the hottest in the 15 years she has lived in Las Vegas. A counselor at a school that's on summer break, Sobosan said she doesn’t step outside during the day if she can help it, and waits until 9 p.m. or later to walk her dogs.

“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. But 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 its hard for your body to cool down,” said Alexis Brignola, an public health researcher at the Southern Nevada Health District.

The searing heat wave gripping large parts of the U.S. also led to record daily high temperatures in Oregon, where it is suspected to have caused eight deaths, the state medical examiner’s office said. More than 142 million people around the U.S. were under heat alerts Wednesday, especially in Western states.

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 90 for most of the region, and forecasters warned the heat index could soar as high as 108. The warning was due to expire at 8 p.m. Wednesday, though forecasters said there may be a need to extend it.

Dozens of locations across the West tied or broke previous heat records over the weekend and are expected to keep doing so all week, although the end of the siege was in sight in some areas.

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 120.

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 don't need a thermometer to tell me that it's hot,” Pell said. “You hear about it in stories and wildlife documentaries. But just for me, I wanted to experience what it would feel like. ... It's an incredible experience.”

Record highs for the date were also hit Tuesday in parts of Oregon and Washington, with Portland reaching 103 and Salem and Eugene hitting 105.

The Oregon State Medical Examiner’s Office on Wednesday confirmed two new suspected heat-related deaths, bringing to eight the total number of deaths during the heat-wave. One was an 83-year-old man in Washington County and the other was a 72-year-old man in Multnomah County. Seven of the deaths were men and one was a woman. The youngest was 33 but all of the others were age 64 and older.

The National Park Service was investigating the third hiker death in recent weeks at the Grand Canyon, where temperatures on parts of some trails can reach 120 in the shade. Bystanders and medical staff on Sunday unsuccessfully attempted CPR on the 50-year-old man, the park service said.

An excessive heat warning continued Wednesday in many parts of southern and central Arizona. Forecasters said the high in Phoenix was expected to reach 114 after it hit 116 on Tuesday, tying the previous record for the date set in 1958.

In Marana, Ariz., near Tucson, authorities were investigating the death of a 2-year-old girl who was left alone in a vehicle on a Tuesday afternoon where the high hit 111. Police Capt. Tim Brunenkant said the car apparently was left running and the air conditioning was functional, but it was unclear how long the girl was by herself.

In Lake Havasu, Ariz., a 4-month-old baby died from heat-related complications Friday after becoming unconscious during a boating trip, the Mohave County Sheriff’s Department said. The temperature that day hit 120.

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 2.7 degrees 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.

In Las Vegas, hotels and casinos keep their visitors cool with massive AC units. But for homeless residents and others without access to safe environments, officials have set up emergency cooling centers at community centers across southern Nevada.

Firefighters in Henderson, Nev., last week became the first in the region to deploy what city spokesperson Madeleine Skains called “polar pods” used to cool a person exhibiting symptoms of heat stroke or a related medical emergency.

Skains said four vehicles in the city of more than 330,000 residents have the devices that are similar to units first put into use a month ago in Phoenix. They can be filled with water and ice to immerse a patient in cold water on the way to a hospital.

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

A new blaze in Oregon, dubbed the Larch Creek Fire, quickly grew to more than 5 square miles Tuesday evening as flames tore through grassland in Wasco County. Evacuations were ordered for remote homes.

In California, firefighters were battling least 19 wildfires Wednesday, including a 45-square-mile blaze that prompted evacuation orders for about 200 homes in the mountains of Santa Barbara County.