FURNACE CREEK, Calif. — For Gary Bryant, the tenth-of-a-mile walk from his modular home to the air-conditioned restaurant where he was working on Saturday was “quite enough” time outside.

Mr. Bryant, 64, knows the risks of summer temperatures in Death Valley. He once collapsed under a palm tree from heat exhaustion and had to crawl toward a hose spigot to douse himself with water.

Mr. Bryant has lived and worked in Death Valley for 30 years, happy to balance the brutal summer heat with the soaring mountain vistas, but even he admits that the high temperatures in recent years were testing his limits. The temperature soared to 130 degrees on both Friday and Saturday and was forecast to hit the same peak on Sunday.

“The first 20 summers were a breeze,” he said. “The last 10 have been a little bit tougher.”

The blistering weekend heat, one of the highest temperatures ever recorded on Earth, matched a similar level from August 2020. Those readings could set records if verified, as an earlier record of 134 degrees in 1913 has been disputed by scientists.

Much of the West is facing further record-breaking temperatures over the coming days, with over 31 million people in areas under excessive heat warnings or heat advisories. It is the third heat wave to sweep the region this summer.

The extreme temperatures that scorched the Pacific Northwest in late June led to nearly 200 deaths in Oregon and Washington State as people struggled to keep cool in poorly air-conditioned homes, on the street and in fields and warehouses.

The same “heat dome” effect that enveloped the Northwest — in which hot, dry ground traps heat and accelerates rising temperatures — has descended on California and parts of the Southwest this weekend.

Sarah Rogowski, a meteorologist with the National Weather Service, said that daytime highs between 100 and 120 degrees were hitting parts of California. Most dangerously, temperatures will remain high into the night, hovering 15 to 25 degrees above average.

“When you start getting those warm temperatures overnight combined with those high temperatures during the day, it really starts to build the effect,” Ms. Rogowski said. “People aren’t able to cool off; it’s a lot harder to get relief.”

She said forecasters were also monitoring looming thunderstorms that could bring lightning strikes and fire risk. Already on Friday, lightning set off a fast-moving fire north of Lake Tahoe, prompting evacuations in California and Nevada, road closures and the partial closure of the Plumas National Forest.

The fire had doubled in size by Saturday as firefighters struggled to contain it. Evacuation orders were also issued in southern Oregon in response to fast-spreading fires there.

The record-shattering temperatures in the Pacific Northwest last week would have been all but impossible without climate change, according to a team of climate researchers. Because climate change has raised baseline temperatures nearly two degrees Fahrenheit on average since 1900, heat waves are likely to be hotter and deadlier than those in past centuries, scientists said.

Excessive-heat warnings blanket most of California, along with parts of Nevada, Arizona, Utah, Oregon and Idaho.

California is facing the most extreme and widespread high temperatures. The agency that runs the state’s electrical grid, the California Independent System Operator, issued pleas on Thursday for consumers to cut back on power use to help prevent blackouts. Gov. Gavin Newsom asked residents to cut their water consumption by 15 percent as he expanded a regional drought emergency to cover all but eight of the state’s 58 counties.

The city of Merced reached 111 degrees on Saturday, breaking the record of 108 set in 1961. Records could be broken this weekend in Fresno, Madera, Hanford and Bakersfield.

Cities and towns across the state’s Central Valley activated cooling centers and temporary housing on Friday.

The city of Sacramento opened three cooling centers and provided motel vouchers to families with small children and older people who had no regular housing.

It was the third time this summer that the city had activated cooling centers, said Daniel Bowers, the city’s director of emergency management. Last summer, Sacramento activated cooling centers only three times during the entire season — the third time was not until September.

This year, the city started its heat response early when a heat wave pounded much of Northern California over Memorial Day weekend.

“That was kind of an eye-opener of how the summer was going to go,” Mr. Bowers said. With its fair share of practice in recent years, he said, the city is well prepared for the weekend temperatures. But the high nighttime temperatures pose particular risks to people who are homeless, he said.

Further down the valley in Modesto, which had a high of 108 degrees on Saturday, the Salvation Army said it had seen an uptick in people seeking shelter.

The shelter is “seeing individuals we normally wouldn’t see — normally people that are OK being in their tents, they’re OK sleeping outside,” said Virginia Carney, the shelter director.

Terri Castle, who has been staying at the Modesto shelter for the past month, said she had spent previous summers living on the street and was worried for people who did not have a place to cool off this weekend.

“When you’re homeless, you’re already out in the weather 24/7,” Ms. Castle said. “And when the sun hits you, it’s hard to find anywhere for shade. You can’t get enough water.” Over her few weeks at the shelter, she said, she has noticed a surge in people seeking relief from the heat.

One man was taken from the shelter by ambulance on Thursday after experiencing heat-related illness. A woman who came seeking water and food “just sat down outside and looked so hot, like she had no energy,” Ms. Castle said.

In Death Valley, the high of 134 degrees recorded in 1913 had been recognized as the hottest temperature ever recorded on the planet. But a 2016 analysis by Christopher Burt, a weather expert, found that the recording was inconsistent with other regional observations, leading him to dispute whether the record was “possible from a meteorological perspective.”

In any case, the recent sweltering temperatures have prompted their own form of tourism. As the number creeps toward 130, people begin lining up to take photos next to the digital thermometer outside the Furnace Creek Visitor Center.

Even on Saturday, when morning temperatures were hovering close to 110 degrees, park visitors could be found playing golf, swimming and hiking in the early morning hours.

Ashley Dehetre, 22, and Katelyn Price, 21, descended into Badwater Basin around 9 a.m. with cooling towels around their necks and three liters of water strapped to each of their backs. Their 33-hour road trip from Detroit and the triple-digit temperatures have done little to dampen their spirits, even after a worried phone call from Ms. Price’s mother revealed that the temperature back home was 66 degrees.

“This view in itself is so awesome, it’s worth it,” Ms. Dehetre said. “So much better than Michigan.”

Zooming past them on the salt flats was Tyler Lowey, who drove overnight from Los Angeles to celebrate his 25th birthday by running 25 miles at the basin, which is the lowest point in North America. The challenge was part of a yearlong set of adventures he was attempting, including biking across the country from Los Angeles to Miami next month. To prepare, he packed his car with plenty of water, amino acid powders and fresh coconuts, which in his time as a personal chef he has found to be the best at combating heat-related fatigue.

Still, after just a mile out and a mile back, he was drenched in sweat and ready to take a break and cool down in his car.

“The heat sucks,” he said. “But I kind of want to bang it out, because the longer I wait, the hotter it’s going to be.”

High up on Zabriskie Point at sunrise, Anshuman Bapna, 42, took in the heat with a bit more reserve. As the founder of a climate change educational platform, he felt compelled to detour his family’s trip, planned from Palo Alto, Calif., to Zion National Park, through Death Valley in order to experience the extreme conditions.

“Heat waves like this are just going to become even more common,” he said. “There’s a bit of a ‘see what you can’ before the world changes.”