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Walking a dog during the summer in Phoenix begins with a test: Hold the back of your hand to the sidewalk for a few seconds. If your hand can’t take the heat, neither can your dog’s bare paws.

Since returning to Phoenix from a 36-hour reporting trip in Grand Canyon National Park, I’ve added another step to my routine: I throw my T-shirt in the kitchen sink and soak it with “cold” water. Park rangers recommend the trick for hot days, and I can testify that it makes a huge difference. During triple-digit temperatures, the only way to experience anything resembling a cooling sensation is to feel moisture wicking off your skin.

You might think that living in the Southwest would automatically build up your tolerance for this kind of heat. But the reality for most people living through summer in the Sonoran Desert is that life unfolds indoors. You scuttle from a temperature-controlled house to your baking car, crank the air-conditioning and, within a few minutes, arrive at another man-made oasis.

With its supermarket and steakhouses, hotels and chilled coach buses, Grand Canyon Village extends this bubble to the edge of the wilderness. For a recent article that appeared in the Travel section of The New York Times, I wanted to understand how the park’s search-and-rescue staff mitigated risk in this borderland, a place where you can buy a milkshake a few steps away from a trail that leads to some of the world’s most rugged terrain.

Much of that work is focused on what rangers call preventive search-and-rescue, known as P-SAR, which amounts to making sure people have the information and supplies they need to get through a hot hike.

Talking to rangers who have watched people reach critical condition within a couple of miles of an air-conditioned food court has a way of changing your perspective on risk. Even as an avid hiker with a few years of desert living under my belt, I realized while reporting this article that I had never really considered the hows and whys behind lifelong trail habits, like snacking on potato chips or dipping a bandanna in the river.

In “Desert Solitaire,” the naturalist Edward Abbey famously railed against the paved roads and utility projects being pushed into remote parts of the country. “Why is the Park Service so anxious” to cater to “the indolent millions born on wheels and suckled on gasoline, who expect and demand paved highways to lead them in comfort, ease and safety into every nook and cranny of the national parks?” he wrote.

For the most part, his argument lost out to what he called “industrial tourism,” and as a result, about five million of us get to see the wonders of the Grand Canyon every year. But topography has put at least part of this impulse in check: If you want to see the canyon from below the rim, you have to walk or hire a mule to take you down. And, as the park’s superintendent, Ed Keable, told me during my visit in June, “Some of our visitors just aren’t prepared for the extreme conditions of hiking in the Grand Canyon.”

Conventional wisdom is that the population most at risk of needing rescue is “YAMs” — young adult males with too much testosterone to heed warnings from nature (or their wise, naysaying friends and relatives). But data from Grand Canyon National Park in 2018 showed that people over 60 needed help most often. The altitude, and the effects of global warming, which push more days over temperatures that we can stand, conspire to make a bad time creep up on you, or accentuate the effects of a chronic health condition.

When I asked one ranger how people who got into trouble in the canyon usually explained how they had ended up in the situation, he answered, “They thought they’d be fine.”

Fourteen years ago, I spent a month floating through the Grand Canyon on a rafting trip down the Colorado River. For my latest trip, I was careful not to tempt disaster and packed a few essentials: a water bladder, a wide-brimmed hat, a pair of sunglasses and good shoes. But after a day of interviews with search-and-rescue rangers, I felt unprepared for the trail. I hadn’t studied maps or plotted out my descent with target departure and return times. Rather than heed their advice to avoid hiking between 10 a.m. and 4 p.m., when the sun is at its most punishing, I overslept and followed the June crowds down into the canyon shortly before 9 in the morning. The temperature was already in the 80s and climbing.

I’m usually an overambitious, seat-of-the-pants kind of hiker. But when I reached Havasupai Gardens, which is four and a half miles into the journey along the Bright Angel Trail, I resisted the temptation to go another mile and a half to Plateau Point, where you can see the blue thread of the Colorado. I turned around instead.

The advice of the rangers had entered my subconscious.