Head into the clouds on a journey through Vietnam's hill country

According to the young Red Dao woman with the incisor decoratively encased in gold, her village of Ta Phin had not seen the sky, let alone the sun, for six long weeks. The winter had been so cold and hard, she explained as we slopped along the muddy track (she in her plastic sandals, me in my hiking boots), that many villagers, including her own family, had lost at least one of their precious water buffalo, animals that cost upwards of eight million dong (£250) to replace.

This level of hardship rather eclipsed our own. Yet there was no denying that our little group was feeling downcast by the lack of visibility in this remote region fabled for its glorious landscapes. Someone had even dared to breathe the word "depressing" as we peered into the monochrome murk. The hotel lobby was heated only by a mean little corner fireplace that had been reluctantly stoked with kindling by the hotel manager in his shiny, too-tight suit.

The only reliable source of heat was bed, where the electric blankets were switched on around the clock; but you don't journey to a hidden corner of Asia to go to bed.

We had just arrived off the overnight train from Hanoi at the railhead town of Lào Cai. From here the only way is up: we had travelled for an hour by switchback road through the pre-dawn blackness to the hill resort of Sapa in northern Vietnam. China's Yunnan province was only 36km away. This region was unknown to Europeans little more than a century ago when French missionaries arrived to convert the local hill tribes (I speculated whether they had won them over with gifts of blankets). After moving the capital of Indochina to Hanoi at the start of the 20th century, the French colonial masters seized upon Sapa as a place to escape the heat of the lowland summer – an amusing irony in our case. Opened to tourism again in 1993, Sapa has become a honeypot, attracting tens of thousands of visitors, including many urban Vietnamese in the rainy summer months.

We thought with longing of the brochure photographs of verdant valleys, rice terraces reaching to impossible heights, and bucolic villages with a scattering of wooden and bamboo houses. We knew that a couple of kilometres away Mount Fansipan rose to a height of 3,143m, the highest peak in Indochina. But we might as well have been searching for Cleopatra's Needle in the haystack of a pea-soup fog in Victorian London. I couldn't help but be reminded of the hordes of Japanese tourists I had once seen staring forlornly at an opaque mass of cloud where New Zealand's Mount Cook should have been. While travellers to the tropics are familiar with the concept of "wet" and "dry" seasons, Sapa seemed to have come up with a variant: the foggy season. Holiday weather is always a lottery, but I wondered if the decision by Travel Indochina to launch a tour to this new destination in winter might have been a gamble too far.

Oh well, there was always Sapa's other attraction, its diverse population of minority peoples. Of the various groups, the principal ones are the H'mong and the Dao (pronounced Dzao) who settled in these hills after fleeing persecution in southern China, mainly in the 18th and 19th centuries. Nowadays village women, tiny of stature, flood into Sapa to sell their handicrafts. The traditional tribal costumes and customs flourish still, and the people's cheerfully coloured clothing and headgear brightened the gloom.

The Black H'mong wear deep indigo tunics with embroidered sleeves and back aprons, dark velvet puttees and pillbox turbans, multi-hooped silver earrings and huge bamboo baskets strapped to their backs. Apart from their lapels embroidered with geometric patterns, the distinguishing characteristic of the Red Dao costume is the astonishing headdress. On top of partially shaved heads, they wear a length of scarlet material wrapped and folded to create a bulging cushion-like turban from which red tassels, tiny bells and silver coins dangle down their backs. Before you get as far as Sapa market, where textiles are displayed on circular cloths rescued from defunct umbrellas in a charmless concrete room, village traders will surround you on the street to display their wares.

Against the odds, the fog and our spirits lifted the next day. As if on cue for the first day of the lunar new year, early morning sunshine flooded the deep balcony of the hotel, illuminating the jagged line of hills all around and revealing the town's attractive ochre-coloured turreted villas with balconies and shuttered windows. Within minutes, the mist had rolled in again, but now it was easy to persuade ourselves of the possibility that rambles between villages scheduled over the next few days would reveal further wonders.

The scenery around Sapa is magnificent, but it was the human drama that proved most gripping. A boy no older than 10 nonchalantly whittled a stick as he rode bareback on a water buffalo plunging knee-deep across the fallow rice paddies on his way home. A man brandishing a curved-bladed knife bounded up the terraces behind his house in search of something meatier than a cabbage. Children played a version of hopscotch that involved the near-impossible feat of picking up a pebble with their bare toes while hopping on one foot. In the background, a sow failed to discipline her litter of squealing squabbling piglets while white ducks did pirouettes on the village pond.

The beating of a drum presaged the most remarkable spectacle of all. We were invited into a sizeable one-room house to observe from behind an open partition a religious ceremony akin to a Mummers' Play. A young man sat on a bench and started to shake violently, then cavort wildly round the dirt floor. When the gyrating dance subsided, three youths moved jointly up and back holding up bamboo sticks painted red for good luck. Like a child at a pretend tea party, the holy man who was directing proceedings mimed the pouring of tea into a row of tiny tea cups and then burned lucky (phoney) money.

The young men turned their attention to the altar next to which painted tableaux and calligraphy panels had been hung. They hopped forward and backwards on one foot, shouting a word that sounded like "hop", which probably meant something along the lines of "May our ancestors' spirits keep our buffaloes warm this year". They scattered corn on the floor before showering each other with edible confetti. All that was missing was an accompanying ethnographer to interpret what we had witnessed, though it seemed reasonable to assume that prosperity and plenty were being invoked for the year ahead.

If prosperity does increase in those villages, it will be due to the tireless efforts of the village women. The male population is largely invisible, especially at festival time when many over-indulge in rice wine. The men in evidence were swanning around on their motor scooters. All the tribal girls learn to sew as children and become expert needleworkers. Gaggles of them can be seen in doorways bent over their handiwork or stitching as they walk, mostly objects to sell to tourists – although, as in 18th-century England, they create their finest pieces for their weddings. If it is true that the best seamstresses are able to make the best marriages, then some of these young women must be betrothed to princes.

These enterprising women have no access to shops or fixed outlets. So they have adopted a peripatetic sales technique that many tourists find exasperating but is undeniably successful. Large groups besiege hikers setting off on footpaths to one of the six or so minority communes accessible from Sapa on half-day or full-day trips. The village women quickly identify the most likely victim and attach themselves accordingly as "friends" and informal guides.

Running the gauntlet is unavoidable, even for those with "Miser" emblazoned on their foreheads. I put my cards on the table from the outset of the first trek, telling my entourage of Red Dao women that I have been to many countries but have at home no souvenirs; I would not be buying. Undeterred and with quiet dignity, "my" group of about four women accompanied me for the entire half-day's amble, answering questions when their English permitted and smiling for the camera. They called our attention to points of interest such as the now-disused rattan bridges straight out of an Indiana Jones film. Some performed feats such as fashioning a sculpture of a horse out of a single strand of grass. When asked about their music, one sang a haunting lament for those "with no mummy, no daddy".

At the end of a trek, it is impossible not to feel some obligation to these eager, smiling people when they produce their embroidered pencil cases, purses and shoulder bags, silver earrings and bracelets. The quality is as variable as the price. Some is just imported Chinese tat. The dye which they make themselves from the nondescript-looking indigo plant grown locally comes off straight away (though can be fixed later by washing in cold salt water). It might go against the grain to encourage this commercialisation of contact with local people. Yet all I can say is that the day I resisted their blandishments, I felt more of a heel than when I handed over a few hundred thousand dong (a trifling amount).

Revived by the watery sunshine and the glow of having made a small financial contribution to an impoverished community, we were eager to travel 18km deeper into Lào Cai province to stay at Topas Ecolodge, run by an expatriate Dane. The conical thatched roofs atop an isolated cone-shaped hill are reminiscent of the distinctive Nó* lá (bamboo hat) worn by Vietnamese paddy farmers. All the clean Scandinavian design inside and efficient heating of the individual lodges proved a welcome haven. The lodge's trekking sheet did not make clear that the short "Buffalo Track" was a route suitable for buffaloes, not humans. Droppings marked the deeply rutted quagmire like so many cairns.

But the panoramic views justified the effort. Stepped terraces reached dizzying heights and created patterns as beautiful and natural as sand ripples under shallow water. These astonishing constructions result from generations of wet rice farmers working from the top down, in case a terrace collapses and obliterates the one below. In winter the puddled mud on these tiny man-made platforms glints in the light. In summer, the emerald greens and golds of the ripening rice must transform these valleys into a place reminiscent of Tolkien's Shire on a Brobdingnagian scale.

Street life in Hanoi had prepared us well for experiencing Vietnam in a way appropriate for a country where gambling is an entrenched part of the culture. Huddles of young boys on Hanoi's back streets bet eyebrow-raising sums of money on impromptu games of chance. In the evenings, old men can be glimpsed through half-open doors intent on their hands of cards, and it is certain they are playing for more than the delicious roasted peanuts used in their cuisine.

Even the most cautious visitor to north Vietnam, city and country, will be forced to play a game of hazard. Stepping off the kerb to cross a road for the first time feels like spinning a revolver cylinder and giving yourself a one-in-six chance of survival. The technique is to wait for a bit of a lull and then step slowly and steadily across the road, establishing eye contact with all oncoming scooter drivers who will lean one way or the other to avoid you. Easy for people with strong nerves, impossible for Westerners who cleave to the supremacy of lollipop ladies.

Clambering into our comfortable bunks on the train at the beginning of the trip, we knew that we were dicing with disappointment. But as we left this mountain fastness behind, the peak of Fansipan finally revealed itself above its girdle of clouds, making us feel especially vindicated in our gamble to visit Sapa in the fog season.