A filmy curtain of rain blows across me. I quickly pull on my hood. Rain, rain, go away! My husband, Ed, and I are only an hour into our hike along Iceland's 34-mile Laugavegur Trail, the Nordic island's most famous, and I don't want showers to ruin the stunning scenery.

Minutes later the rain stops and two fat rainbows arc across the sky, twin kaleidoscopes of color brushed across an already-breathtaking canvas. I slide off my hood and begin snapping photos. Five minutes later Ed tugs on my sleeve. It's time to move on. We have to reach the Hrafntinnusker hut before dark, and it is still miles away.

The trail inches upward some 1,500 feet, but we barely notice the climb. Gleaming black chunks of obsidian wink at us as we pick our way across a lava field, kicking aside pockmarked lumps of pumice. Eggy-smelling clouds of steam puff from innumerable holes drilled into the earth, reminding us that Iceland, despite its name, is actually a fire-breathing volcanic island. And everywhere we turn we're greeted with expansive views of impressive rhyolite mountains: enormous buff-colored mounds streaked with terra cotta, butter and emerald.

About halfway to the hut, great gusts of wind sweep across the narrow, rocky ridge we're ascending. Unprepared and unbalanced with 20 pounds strapped to my back, I crouch down to avoid being blown away. Somewhere on today's hike — perhaps right here — is the trail's highest crossing. Although it's just 3,600 feet, Iceland's arctic environment makes it feel much higher. Weather conditions can change without warning.

We make it off the ridge safely and I resolve to stop taking so many photos so we can quicken our pace. It proves a wise move. The path unspools across a small snowfield, then past a memorial for a 24-year-old who perished on the trail. Then, with the hut in sight, the heavens open and it begins to pour.

Minutes later, huddled around the hut's warm stove with a handful of other hikers, we prepare to bring our freeze-dried dinners back to life.

The Laugavegur Trail connects Iceland's Landmannalaugar and Þórsmörk Nature Reserves, rolling through lava fields and glaciers, past natural hot springs, and across both black arctic deserts and lush valleys. Widely considered one of the world's most beautiful hikes, it takes most people several days to cover the distance, necessitating overnights in rustic mountain huts or campgrounds. During prime hiking season in July and August, some 100 people strike out from Landmanna­laugar daily.

Ed and I are here in mid-September, when hiking season is winding down. There are no crowds, which is great. But it's also the time of year when the weather is more volatile.

Cold streams and brisk rain

Frímann Ingvarsson, the Hrafntinnusker hut warden, asks us about our day. We excitedly tell him about all of the rainbows we saw, which we assume is a rarity.

"It's unusual to hear lightnings and thunders in Iceland," says Ingvarsson. "But we always have rainbows."

The next morning, Ingvarsson says we should check out the ice caves, a 20-minute hike from the hut. Intrigued, we head out. Soon, after cresting a stony hill and skittering down its snow-covered backside, we spy a series of sparkling ice caves sweating from the hot springs bubbling outside their yawning maws. A bright-yellow sign yells: "Danger! Watch out for falling ice in the ice caves." Ingvarsson said one hiker met his demise when a dripping cave collapsed onto him, so we're content with taking photos from a distance.

Back on the trail, the miles unwind as we hop, skip and jump over innumerable streams; scramble up and down black, sandy hills; and carefully pick our way down scree-filled slopes. The going is strenuous, but the otherworldly vistas make up for it.

For our third morning, the guidebook says several glacial river crossings await. The hut warden says we have a choice: take the dowdy main route, with just two river crossings, or the scenic alternate, which has three. "One is the Cold Crotch River," she says with a wink. "And its name is for real. When you're nearing the next hut, you'll see Porno Mountain." Clearly, Icelanders call it as they see it.

Ed and I prefer warm crotches, so we set out along the official route, where the rivers' icy waters barely top our kneecaps. But we battle a soaking rain followed by stiff headwinds that force our heads downward, relegating us to views of our boots trudging through shifting black lava ash. When we reach the point of exhaustion, the wind abruptly stops. The pewter sky brightens. And a peak emerges from the haze, sporting a rocky pillar. "It's Porno Mountain!" shouts Ed.

After dinner, the weather now bright and balmy, we strike out on a short side trail with others we'd met along the way: two Canadian couples, a young Israeli and three Spaniards. We marvel at the landscape and bemoan the fact that tomorrow we'll reach Þórsmörk and the end of the trail.

Þórsmörk or bust

Day four. Steel skies welcome us onto the trail, but that doesn't dampen our spirits. The morning brings a vigorous hike up and down the mountains. At one point, the trail chipped into the mountain's massive flank is so narrow and steep that a chain railing has been hammered into its side for hikers to grab.

Soon the landscape morphs into flat, desert-like terrain scarred with oddly shaped rocks and scruffy vegetation. I draw the word "HOLA" and a smiley face in the sand; it's a message for the Spaniards, who prefer to sleep in and so are behind us. Next up is another river ford, followed by a surprise: an uphill hike through forested terrain.

Some 25 percent of Iceland was once covered in trees. But when the Vikings landed there 1,000 years ago, they cut down most of them. Reforestation efforts finally began in the 20th century, when only 1 percent of forestland remained, but the task is proving herculean. Today, despite planting millions of trees, the percentage of forestland has only risen two or three percentage points.

Shortly before reaching Þórsmörk, we bump into a tall Icelandic woman hiking with her kids. She mentions that she once won a race along the Laugavegur Trail, running the arduous 50-kilometer route in a mere five hours and change. Impressive, yes. But we'll take our four days.

Our companions head back to Reykjavik, Iceland's capital, but Ed and I decide we're not finished yet. There's one more possible hike here — continuing on to Skógar, south of the Eyjafjallajökull volcano and glacier. Billed as a 10- to 12-hour trek, it leads you over the Fimmvörðuháls mountain and past the craters formed by Eyjafjallajökull's famous 2010 eruption, which halted European air traffic. If we tackle this stretch tomorrow, we'll be treated to the rare sight of relatively fresh volcanic detritus. It's a no-brainer.

The following morning, none of the young employees in the Þórsmörk dining hall can tell us if today's weather is safe for hiking to Skógar. As this trail climbs more than 3,000 feet, we don't want to head up the mountain if the forecast is poor. With no good intel, but clear skies, we take a chance and strike out.

The toughest part of the hike comes immediately, as the path pitches us steeply skyward. At times we're forced to hike along ledges so narrow and rocky, I'm positive mountain goats would have trouble here. In other spots, we scrabble along the sides of sheer cliffs, clutching chains welded to their flanks. This is serious stuff.

When the terrain finally flattens out and we reach the impressive volcanic formations we've been waiting to eyeball, a soft, white fog envelops the trail. All we can see are gray smudges encased in marshmallow puffs. Every so often the fog rises for a few seconds — just enough time to let us spot the next trail marker and move a few feet forward.

We reach a melting tongue of glacial ice and spot the next marker on its far side. We slip and slide across the ice, becoming soaked in the process, only to be trapped by the fog when we finally reach terra firma. Unable to see where to go next, we huddle together, shivering, for who knows how long.

Eventually the fog lifts, and we hike out of the madness and back downhill to the Skógar trailhead, passing 26 waterfalls in this section dubbed "Waterfall Way."

Later that night, clean and dry in a Reykjavik hotel, we reflect on our hike. No, we did not get to see the undoubtedly impressive handiwork of the Eyjafjallajökull volcano. But we saw rainbows and ice caves; trudged across dramatic stretches of lava ash, snow and glacial ice; and clung to mountainsides by thin, metal cables. The hike was thrilling and scary, and beautiful beyond words.

Melanie Radzicki McManus lives near Madison, Wis.