A 50-year-old woman has gone missing from a hiking trail in San Diego after separating from her group as excessive heat gripped the area over the weekend, authorities said.

Diem Le Nguyen was hiking on Nighthawk Trail on Black Mountain near 9711 Oviedo Way with a group when they stopped halfway along the trail at around 8 a.m., the San Diego Police Department said. 

Nguyen left her group and continued alone to finish the trail, police said.

Nguyen contacted her group at around 9:30 a.m. to let them know that she had reached the end of the trail. Police said the group has not heard from her since.

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Diem Le Nguyen on hike

Police said Nguyen appears in this photo taken on Sunday before she went missing. (San Diego Police Department)

"Due to the weather and difficulty of the trail, she is missing at risk," police said of Nguyen.

Diem Le Nguyen

Diem Le Nguyen, 50, was reported missing Sunday after disappearing during a hike on Black Mountain's Nighthawk Trail in San Diego. (San Diego Police Department)

Officials in California warned of potential triple-digit temperatures affecting inland Los Angeles and inland San Diego over the weekend. 

The National Weather Service issued an excessive heat advisory for parts of Southern California through Sunday evening.

Nighthawk Trailhead sign

Nguyen disappeared on after separating from her group to continue on Nighthawk Trail alone, authorities said. (FOX5 San Diego KSWB)

"With the heat advisory this weekend, it's extremely hot, dehydration is very much a big factor for this," Officer Darius Jamsetjee told FOX5 San Diego. "There’s not a lot of shade on that trail, it’s just low-lying brush. So the heat will get to you very quickly, plus the elevation gain of a couple hundred feet from here."

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Nguyen was last seen wearing a black shirt with a pink heart on the front, black pants, a brown hat and sunglasses, and a backpack, police said. She was described as a 50-year-old Asian female, standing about 5-foot-1-inch tall, 105 pounds, with black hair and brown eyes. 

search and rescue base

Search and rescue teams are searching for missing hiker Diem Le Nguyen near the Nighthawk Trail on Black Mountain in San Diego. (FOX5 San Diego KSWB)

Police shared a photo of Nguyen they say was taken on Sunday before she disappeared.

Authorities have used helicopters and drones to search for Nguyen by air, while the sheriff's search and rescue team, along with volunteers, FOX5 reported.

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Authorities asked anyone with information related to Nguyen’s whereabouts to call 911 and reference Case Number 24-50182.