Mt. Rainier stood shockingly tall and broad, a shaggy old bison of a mountain surrounded by coyote-scale peaks. However close or distant you’re standing, Rainier just looks so impossibly big it’s a little hard to believe it’s real. It rises anywhere from 8,000 to 11,000 vertical feet above hikers on trails around its base. Few North American peaks have visible relief of two vertical miles. You naturally react as you might to a full-blown, heat stroke-induced hallucination: Compelled to believe your eyes, you nonetheless struggle with the nagging intuition that the delicate fruit that is your frontal lobe has spoiled badly in the heat.

We hiked across Spray Park, gently undulating, sub-alpine meadows at about 6,000 feet above sea level that are renowned as one of the Pacific Northwest’s power spots for wildflowers. We made this trip in the first week of August, at the peak of flower bloom. Lupine, beargrass, phlox, goat’s beard, pink monkeyflower, and other wildflowers in a mosaic of yellow, white, pink, and purple carpeted the ground against the backdrop of Rainier’s brilliant snow and ice. Hoary marmots chomped on plants just a few steps off the trail. We dropped our packs at great tongues of snow extending 300 feet down gentle slopes, leftover from the heavy snowfall of last winter and spring, and our kids “skied” laps on the snow in their hiking boots.

Besides the magic of Spray Park, our three-day hike featured giant slugs—one of them as long as a child’s hand—and a big pile of freshly deposited black bear poop; views of the largest glacier in the Lower 48, the Emmons, and a close-up look at the Carbon Glacier, which is the longest (5.7 miles) and thickest (700 feet) river of American ice outside Alaska, with the lowest terminus (3,500 feet); lots of waterfalls and creeks roaring, foaming, and gray with glacial silt; and an exciting, bouncy crossing of the suspension bridge above the Carbon River. It’s one of the greatest long-weekend backpacking trips in Mt. Rainier National Park or the entire Pacific Northwest.

Rainier has a fascinating back story involving Pineapple Express storms, deadly lahars (or mudflows), and climate change. A few summers ago, I backpacked here to write a story for Backpacker Magazine about record floods that struck the park in November 2006, during a storm that dropped an incredible 18 inches of rain in 36 hours, causing mind-boggling devastation. Roads were wiped out across the park, which remained closed to private vehicles for an unprecedented seven months; one gully carved by floodwaters across WA 123 was 70 feet deep. I saw 100-foot-tall trees with trunks that two adults couldn’t join arms around piled up like matchsticks in creek beds—and those piles stretched for miles, consisting of thousands of trees. I visited what was left of one backcountry campsite—since relocated—buried under several feet of dried, cracked mud, boulders, and trees, the debris from a lahar. Fortunately, no one was camped there when it hit.

That storm’s devastation was magnified by complex dynamics involving unusually warm, so-called Pineapple Express storms striking in late fall and early winter, receding glaciers, and the unstable soils found on heavily glaciated volcanoes like Rainier. Climate experts predict that as average temperatures rise in coming years and decades, we’ll see more such storms and floods. Some believe we’ve already entered this new climatic regime: the Pacific Northwest saw three “100-year floods” in the 11 years between 1995 and that November 2006 super storm.

I’ll write more about this trip and Rainier’s unsettling future in my book “Before They’re Gone,” about taking my kids on wilderness adventures in national parks facing various threats from climate change, to be published by Beacon Press.

I’ll also write a full-length feature story about this backpacking trip for TheBigOutside.com, at a later date. For now, check out a photo gallery and video from that trip.