The National Park Service warned visitors about excessive heat after the death of a hiker in the Grand Canyon Sunday.
CNN  — 

A woman who embarked on a multi-day backpacking trip through the Grand Canyon National Park died on a trail Sunday, the park said.

Delphine Martinez, 59, of Window Rock, Arizona, “became disoriented and later unconscious” while hiking along the Thunder River Trail and was not able to be resuscitated, a release from the park said.

While the park did not release Martinez’s cause of death, it noted that high temperatures in the inner canyon were well over 100 degrees on Sunday. At Phantom Ranch, which lies at the bottom of the Grand Canyon, the high temperature reached approximately 115 degrees, the release said.

Martinez died about one mile from where the Tapeats Creek and Colorado River converge, the parks service said. Her death is being investigated by the parks service and the Coconino County Medical Examiner.

“Park rangers at Grand Canyon National Park urge visitors to Grand Canyon, especially inner canyon hikers and backpackers, to be prepared for excessively hot days in the coming weeks,” the release said.

Temperatures on exposed parts of the trail can reach more than 120 degrees in the shade during the summer, and park rangers caution people not to hike in the inner canyon during peak hours of heat between 10 a.m. and 4 p.m.

“Hiking in extreme heat can lead to serious health risks including heat exhaustion, heat stroke, hyponatremia, and death,” the release said.

Another Arizona hiker died Monday after suffering heat exhaustion while hiking near the Spur Cross Trailhead, about 40 miles north of Phoenix, officials said.

Arizona, like much of the West, has been stifled under extremely high temperatures over the last few days as a heat wave sweeps across the region. The blistering temperatures have led the National Weather Service to issue an excessive heat warning for the Grand Canyon area until Wednesday evening.

Heat is the top killer among natural disaster deaths, studies show. Extremely high temperature can put significant strain on the heart or making breathing more difficult, and it can also cause a person to dangerously overheat to the point of severe illness – or even death.