A heat wave stretched across the Southwest on Saturday, prompting warnings for some national park visitors to drink plenty of water and avoid long hikes under the sun.

With temperatures at Phantom Ranch on the bottom of Grand Canyon National Park possibly soaring to 113 degrees Fahrenheit, park visitors were urged not to hike down into the canyon from either rim. The warning was to run through Sunday.

At Lake Mead National Recreation Area in Nevada, officials close the Goldstrike Canyon and Arizona Hot Spring trails from May 15 through September 30 due to the high heat that bakes the trails and poses problems for hikers. In 2013, there were 17 incidents, which resulted in one fatality, 31 patients and five medical transports. In the first seven months of 2014, there were 37 incidents, resulting in three fatalities, 35 patients and 13 medical transports, the park reported.

At Joshua Tree National Park in California, while not related to the current hot weather, a dog died on the Lost Palms Oasis Trail a week ago from the heat, according to park officials.

While pets are not permitted on trails, two men from Long Beach, Calif., took the animal with them on a seven-mile desert hike last Saturday, May 28.

"At approximately 12:45 p.m., other hikers came into the Cottonwood Visitor Center and reported that a four- or five-year-old black Labrador retriever dog was in trouble a little over a mile from the trailhead. Park rangers hiked to the site, where they found the dog already dead. They carried the body out on a litter," a park release said. "One of the two men was also showing signs of heat-related illness. Temperatures on Saturday afternoon reached 81°F (27°C) in the Cottonwood area of the park. The desert environment can be deadly, especially from May through September, when temperatures in the park often soar above 100°F (38°C)."

At Joshua Tree, visitors are "cautioned to avoid physical activity in the heat of the day and to carry abundant water and salty snacks. Staying well hydrated helps the body cool itself through sweating, and salty snacks replenish lost electrolytes."