Dangerously high temperatures are forecast for national parks, including Death Valley, this weekend/NWS

A dangerous heat wave is sweeping parks in the West this weekend, bringing triple-digit temperatures to Death Valley, Grand Canyon, and Zion national parks, among other park units, and prompting rangers to caution visitors about the heat.

Across those three parks the National Weather Service is predicting temperatures will move well past 100 degrees Fahrenheit in the coming days. Heat advisories were posted for all three parks.

"It's the hottest days of the year this weekend, maybe 110 in the canyon. We're just really pushing messaging to folks about proper hydration," Zion spokesperson Jeff Axel said Friday.

Just to the south at Grand Canyon, there already has been one heat-related fatality this summer. A 49-year-old California woman died on June 26 as she and her husband and a friend hiked down the South Kaibab Trail to spend a night at Phantom Ranch. The trio was about two-thirds of the way down the trail to Phantom Ranch when the woman collapsed, not far above the Tip Off resthouse.

That wasn't the first heat-related incident at Grand Canyon this summer, and conditions in the coming days could bring more. In a bid to educate visitors about the dangers of the heat, PSAR rangers -- preventive search and rescue rangers -- were being posted at key points to talk with hikers.

"In anticipation for an excessive heat wave this weekend, we're definitely getting our PSAR staff out on the trails, actively contacting people, making sure they're having good hiking plans for the day and they have a reasonable plan for what they want to do and try to accomplish," said Joelle Baird, the park's spokesperson. "That's definitely a big priority this weekend. Getting that messaging out and just warning people about the heat."

Baird said the forecast calls for high temperatures in the mid-90s on the South Rim at 7,000 feet, "and on average it's about 20 degrees warmer at the bottom, so it could see shade temperatures as high as 115, 120."

"Of course, you also have to factor in the dark rocks that get super-heated from the sun. A lot of times the ambient air temperature with this type of year and temperatures can be in the 130's and 140's," she added.

Still, the heat doesn't seem to be dissuading hikers from heading down the trails into the Inner Gorge.

"It's crazy to think that we still have that kind of visitor," said Baird. "We have signs that are posted warning people of the excessive heat at the trailheads, we have PSAR staff usually stationed about a mile or two down trail to check in with hikers as they go by.

"Our tactics really haven't changed that much. We're still seeing heat-related emergencies, people are unprepared, they don't have the essential items that they need to have a successful hike. We're still seeing a need for having a strong presence on the trail and using firm messaging to warn people."

Death Valley has a notorious record with heat-related emergencies, including more than a few deaths believed to be heat related.

In June 2016, a 60-year-old German motorcyclist died near the southern end of the park at a time when daily temperatures at Furnace Creek went as high as 118 degrees Fahrenheit. When rangers found him they didn't even try to resuscitate him because it was obvious he had been dead for an extended time, park staff said at the time.

That June was the hottest on record in the park, with the average daily temperature registering 101.9 degrees Fahrenheit. Later that summer, in August, another park visitor died in the heat, also in the southern end of the park.

Death Valley holds the record for highest officially recorded temperature on the planet: 134 °F back on July 10, 1913.

While the temperature in the park is expected to reach 126 degrees Fahrenheit on Sunday and Monday, officials don't expect that record to fall. Still, it's dangerous to be out in the park during the middle of the day.

"Within the past few weeks we've had a handful of emergencies related to heat, and all three of them were people who were exerting themselves in the heat of the day," said Brandi Stewart, the park's education and outreach program manager. "From what I understand, this weekend is the highest temperatures that we have had all year, or are forecast to be."

Signs posted at trailheads in Death Valley warn visitors about the dangers of hiking in the heat of the day and recommend that they don't hike after 10 a.m. 

In years past, there have been instances on particularly hot days when folks would see if they could fry an egg on the sidewalk near the visitor center. While it might get hot enough to do that this weekend, visitors are urged not to try.

"It became an issue with coyotes getting leftover egg remnants," Stewart explained.