You could risk your life if you walk across Badwater in Death Valley at midday this weekend due to record heat/Rebecca Latson file

Editor's note: This updates with Santa Monica Mountains NRA officials urging visitors to avoid the hottest periods of the day and to leave dogs at home.

Record heat across the southern tier of the country and in West is creating deadly conditions for some national park visitors, including those at Death Valley National Park where the key message was "Travel prepared to survive."

Already this year at least four park visitors have died as a result of the oppressive heat: Two at Big Bend National Park, one at Grand Canyon National Park, and one at Death Valley.

With daily high temperatures well above 100° Fahrenheit expected to persist into next week, caution was the message parks were sending out.

"Temperatures reach over 110+ every day along the Rio Grande and throughout the desert areas of Big Bend. These are extremely dangerous/deadly temperatures! Hikers should be OFF TRAILS in the afternoon," warned a message on Big Bend's website. "Stay hydrated. Limit your exposure."

At Death Valley, where the temperature at Furnace Creek could climb to 126° Fahrenheit on Saturday, the message was similar:

"Expect high temperatures of 110°F to 120°F+ (43°C to 49°C+). Drink plenty of water and carry extra," that park's website warned. "Avoid hiking, do not hike after 10 a.m. Travel prepared to survive. In the case of a heat related illness, get to a cool place and seek help immediately."

At Santa Monica Mountains National Recreation Area in California, officials on Friday warned hikers to avoid the hottest periods of the day and to leave their dogs at home.

The mountains and coastal areas of the NRA were forecast to be within “High” or “Extreme Heat” Friday, with some places reaching temperatures as high as 115° Fahrenheit.

“Heat is the No. 1 cause of weather-related fatalities in the U.S., so please limit outdoor activities to the early or later part of the day when the temperatures are not as high,” said David Szymanski, park superintendent. "In addition, we also want to prevent what we see too often during this time of year — dogs succumbing to the effects of the summer heat on the trail. Dogs are more susceptible to heat stroke and can literally die within minutes. Please leave them at home in the air conditioning.”  

The National Weather Service issued an excessive heat warning through the weekend for southern Utah, including Zion National Park and parts of Glen Canyon National Recreation Area. Lake Powell in Glen Canyon NRA could see a 115° Fahrenheit reading next week, the Weather Service said.

Visitors to Organ Pipe Cactus National Monument in southern Arizona faced the same excessive heat warning, with high temperatures there to approach 110° Fahrenheit this weekend, while Grand Canyon National Park's forecast was even hotter, with highs expected to approach 114° Fahrenheit inside the canyon.