By DORANY PINEDA, TY O’NEIL and JOHN LOCHER

DEATH VALLEY NATIONAL PARK, Calif. (AP) — When the running gets hard in this desert dubbed “hell on Earth,” Danny Westergaard tells himself: “Slow and steady” or “smooth as butter.”

For 18 years, Westergaard, 66, has braved the scorching summer heat of California’s Death Valley in an ultramarathon billed as the world’s toughest. Last week, 99 runners from across the globe embarked on a grueling 135 mile competition from the lowest point below sea level of North America to the trailhead of the highest peak in the contiguous U.S. They had 48 hours to do it. Few have completed the competition as many times as Westergaard, a retired aerospace project manager, though finishing is not a given.

“It’s just become like a summer ritual and a family reunion,” he said. “I feel at home when I’m here. It’s my tribe.”

For the 37th year, the Badwater 135 Ultramarathon challenged athletes to withstand stretches of this dry, searing desert. The race takes place in July, when temperatures have soared into the 130s F. Even as a place of extremes, Death Valley is not immune to global warming. Seven of its hottest summers have occurred in the past 10 years, according to the National Park Service. And if planet-warming greenhouse gas emissions continue at their current pace, more places could experience its broiling temperatures.

Over two days, Westergaard would trek up and down mountain ranges, past sand dunes and salt flats, through quaint towns and vast desertscapes amid temperatures as high as 117 F. He tried to smile throughout, even when he felt miserable.

“It just lifts you up,” he said of smiling so others smile back.

First night: The race begins

At 8 p.m., the first wave of runners take off. Westergaard jogs up a ramp into the pale light of dusk. It’s 113 F, and it feels like a blow dryer to the face.

Leap frogging in a van behind him is his cheer squad and support crew – Jennifer Drain, his smiley cousin back for the 17th year, and daughters Meagan, who has attended before, and Madison, a first timer. The crew, who playfully call Westergaard “wiener dog,” are hauling everything he needs: food, ice, water, electrolytes.

This heat can kill. Soaring body temperatures can lead to organ failure and strain the heart, especially for people with heart disease, and cause heat stroke. To prevent that they keep him cool. They spray mist on him and pour ice into his hat and a bandana wrapped around his neck. His drinking water is ice cold.

A few hours in, Meagan asks her dad if he’s peed. “Long stream,” he responded of his amount of urine. Staying hydrated is critical. As he sweats, he’s losing liquids that can critically stress kidneys if not replenished. Dehydration can cause organs to fail from lack of blood, oxygen and nutrients, leading to seizures and death.

No runners have died doing the competition, but heat-related issues are common, said Megan Dell, the race’s medical director. Stomach issues can lead to vomiting and dehydration. Hyponatremia — which happens when your blood’s sodium is too low — has sent runners to the hospital.

Westergaard has learned to embrace the rollercoaster. One moment he feels like Superman — the next he could be throwing up on the side of the road, questioning if he’ll make it. “You just suck it up, just like in life, and get through the lows, and it always gets better.”

The next day: Running through “the oven”

The runners dash toward mile 50.8, the critical cut off point they must get to by 10 a.m. or be eliminated. The sun is peaking over the mountains, casting a warm glow over dune fields. It’s 85 F.

“Living the dream, ey?” Westergaard said with a smile, his perky strut now a droopy shuffle.

He pours water on his face and arms and munches some watermelon. Madison paces behind him as they crack jokes. “Get er done! Junior wiener in training!” Meagan yelled.

Westergaard makes it to the cut off point before 9 a.m. It’s 90 F.

Mile 56: After moving for 14 hours straight, Westergaard rests and eats some avocado toast. “Great! Let’s motor!” he said after 10 minutes sitting on a chair.

Miles later, he begins his descent into “the oven” that is Panamint Valley, usually the hottest part of the race during the hottest part of the day. It’s 96 F and the heat sizzles from above and below. Westergaard runs on the white line on the road because it’s cooler. In hotter years, the asphalt got so hot the bottoms of his shoes felt sticky on the ground.

Westergaard trains year round to acclimate to the heat. As he gets older, he doesn’t tolerate heat as well and has slowed down. His two-hour sauna sessions are now one, and he runs a few times a week instead of daily.

“I’m just out there longer,” he said, “but still getting it done.”

Tony Wolf, kinesiology professor at the University of Georgia, said aging adults generally have reduced heart function compared to younger adults. When combined with the cardiovascular demand of exercise and heat stress, it can cause difficulties.

There isn’t much research about how the bodies of fit older adults, including competitive athletes, regulate internal temperature. “There aren’t a ton of people in their 60s and older who are doing those kinds of events,” said Wolf.

Studies focused on adults before and after a training program found that exercise improved heart function and thermoregulation. That could suggest that the heart and thermoregulation impairments linked to aging are largely mitigated by lifelong fitness, Wolf said.

Second night: Sleepy hallucinations

The runners are spread out now, their flashing lights twinkling in the distance. This night is the toughest for Westergaard as sleep deprivation sets in. He zigzags on the road, barely awake. The runners ahead of him look like they’re running toward him.

In past years, his hallucinations have included people luring him to rest on couches that were actually bushes. Another time, he struck up a conversation with a kid skateboarding by him with a dog. And once, he watched for hours as a guy swung off the edge of the crescent moon, waving down at him.

“It was just clear as day,” Westergaard said of the hallucination.

At 3:10 a.m. at mile 98, he sleeps for 15 minutes under the moonlight.

“No one really quite understands” why he does this, said Madison.

Final day: The push toward the finish

At 11:50 a.m. and around mile 123, Westergaard shuffles through the town of Lone Pine. Mount Whitney, the tallest peak in the continental U.S., soars some 14,500 feet into the blue sky.

A crowd claps and cheers as he runs by.

“Go Danny, go!” yelled a man.

It’s 92 F as he approaches the final 4,750 foot mountain ascent to the finish line. Westergaard is walking at a snail’s pace and says he’s falling asleep. But his smile hasn’t waned.

“We’ve come a long way,” Westergaard said, Madison pacing behind and spraying him.

“Long way for a burger!” she responded. They giggle while thinking about the veggie burger they’ll buy upon finishing.

Then he does, crossing the finish line with his crew at exactly 45 hours and 29 minutes.

It was his most special Badwater 135 race by far, he says misty eyed, having Meagan and Madison at his side.

The Associated Press receives support from the Walton Family Foundation for coverage of water and environmental policy. The AP is solely responsible for all content.

For all of AP’s environmental coverage, visit https://apnews.com/hub/climate-and-environment