GRAND CANYON NATIONAL PARK, Ariz. (AP) - Park visitors are being cautioned about dangerous heat expected early next week after several recent heat-related emergencies in the inner canyon that claimed the lives of three hikers.

The National Weather Service placed the Grand Canyon under an extreme heat watch from midday Monday through Tuesday with temperatures forecast to hit or surpass 110 degrees Fahrenheit (43 degrees Celsius) at low-elevation Phantom Ranch.

Hikers are strongly urged to stay off trails during peak midday hours, the National Park Service stated in a recent advisory issued after a surge in heat-related problems.

An extreme heat watch was already active on June 16 when two hikers ages 67 and 68 were discovered deceased on the North Kaibab Trail, considered the toughest of the main inner-canyon routes. Officials believe both succumbed to heat illness.

A third hiker age 72 died June 12 on the South Kaibab Trail after suffering heat-related illness, the Park Service confirmed.

Roughly 90 miles south, visitors and residents of Oak Creek Canyon were ordered to evacuate late Friday when a wildfire consumed hundreds of acres just north of Sedona, Arizona.

Much of the western United States from the Rockies to the Pacific Coast experienced above-average temperatures Saturday and faces even hotter conditions early next week. Authorities noted that the extended dry heat and low humidity have raised wildfire risk across the region.

Extreme heat raises dangers for Grand Canyon hikers

Park and weather officials stress that conditions can be misleading. Temperatures on the rim are frequently 20 to 25 degrees cooler than those hikers encounter on the canyon floor.

It is simply a hot environment at the bottom of the Grand Canyon, said Justin Johndrow, a meteorologist with the National Weather Service office in Flagstaff. He noted the area is entering its hottest stretch before monsoon rains later in summer bring some relief.

Descending hikers may enjoy cooler air and easier terrain at first, yet they must later climb thousands of feet in elevation through far hotter canyon-bottom conditions. Heat illness can therefore develop unexpectedly.

That climb is already demanding on a mild day, Johndrow said. Adding temperatures of 105 to 110 degrees creates serious health risks.

Park staff recommend avoiding strenuous hiking during the hottest midday hours.

Wildfire near Oak Creek Canyon threatens safety

A federal interagency team joined by more than a dozen local agencies is battling the blaze that has scorched about 500 acres of steep rugged terrain near Oak Creek Canyon, according to Dick Fleishman, fire information officer with the southwest area complex incident management team.

The fire remains centered in the Red Rock-Secret Mountain wilderness roughly seven miles north of Sedona yet has begun spreading into Coconino National Forest. Crews are working to contain the flames, keep them from advancing toward evacuated areas of Oak Creek Canyon or Sedona, and prepare for any further movement.

Fleishman cited the steep slopes, nearby property at risk, the extreme heat firefighters face, and the threat of post-fire flooding as key concerns with the Pocket Fire.

This incident grew complex rapidly, he said. We aim to limit its overall size.

About 30 miles of the neighboring state highway were closed in both directions. Evacuations were ordered for visitors and residents near Oak Creek Canyon, a destination that draws millions of people annually.

For June 20, Fleishman said of his drive through the area, I have never seen it that quiet.