A man was found dead on a trail in Texas' Big Bend National Park.
According to the National Park Service, the park's communications center received notice of the fatality along the Chimneys Trail on Thursday at 7:45 p.m. local time.
Rangers responded and a 75-year-old Houston man was located approximately half a mile from the trailhead.
The park service said there was no obvious cause of death.
"Big Bend National Park staff and partners are saddened by this loss," Deputy Superintendent David Elkowitz said in a statement, "and our entire park family extends sincere condolences to the hiker's family and friends."
The Chimneys Trail is a moderate difficulty 5-mile round trip hike to prominent volcanic formations in the western desert of the park.
The agency noted that summer weather in Big Bend is extremely hot, with temperatures over most of the park reaching more than 100 degrees Fahrenheit by late morning and increasing to "exceedingly dangerous levels" until long after sunset.
On Thursday afternoon, the temperatures along the trail exceeded 104 degrees Fahrenheit.
"Park Rangers wish to remind all visitors to be aware of the dangers of extreme heat. Hikers should be prepared to carry and drink one gallon of water per day and to plan on being off desert trails by noon," the park service concluded.