Someone once told me that summer in the Arabian Gulf is “like standing under a hairdryer and then throwing a bucket of water over yourself” – a pretty accurate description of the suffocating heat and humidity of Muscat, the capital of Oman.

Not so in Salalah. The country’s second city is in Dhofar province, about 1,000km southwest of Muscat. From July to September, monsoon clouds from India descend on Dhofar’s coastal fringe, bringing light drizzle and heavy fog. The khareef, as it’s known locally, transforms the rugged mountains and valleys from parched brown to lush green.

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The city itself consists of a jumble of low-rise buildings, mosques and minarets, a corniche dotted with palm trees and thriving plantations of coconuts, papayas and bananas. Its men dress in brilliant white dishdashas with an embroidered kuma (cap) or massar (turban), the women wear jet black abayas and, Salalah being more traditional than Muscat, often a veil.

It is still humid, but temperatures of around 27 degrees Celsius make this southernmost tip of the sultanate popular with holidaymakers from the Gulf.

Western travellers tend to visit in the dry months – October to May – when the skies are blue and the seas calm, but seeing Salalah during the khareef offers an unusual glimpse of the Gulf. With the recent opening of a shiny new airport, though, and the arrival of a handful of top-notch resorts, this little pocket of paradise won’t stay a secret for much longer.

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On the advice of our Bedouin guide, Mussallem, we head to Wadi Darbat, an emerald green valley more reminiscent of Ireland than Arabia, about 80km east of the city. As we drive into the valley, children hang out of the windows of cars coming the other way, enjoying the rare pleasure of rain falling on their faces, while families gather to barbecue and stroll beside the wadi’s small stream.

Dhofar is also home to the Boswellia sacra tree, source of the ancient world’s most prized commodity: frankincense.

“It was once more valuable than gold,” Mussallem says, as we arrive at a wadi full of frankincense trees near Mughsail, a windswept stretch of coast about 48km west of Salalah. He scrapes the bark of a scraggly tree and sticky white droplets of sap start to appear.

Since the seventh century BC, people have collected and dried these droplets, which give off a heady aroma when burned. The flourishing trade saw huge quantities shipped via the Red Sea to Egypt, Africa and Europe, and east into the Arabian Gulf and on to India and China.

The ancient frankincense port at Khor Rori remains accessible. Atop a small hill above the picturesque freshwater creek, separated from the sea by a sandbank that was once a bustling entrepot, lie the excavated ruins of the city of Sumhuram, founded in the third century BC. As wild camels and flamingos gather at the creek to drink, we explore the maze of buildings, temples and wells encircled by once-impregnable limestone walls.

Back in Salalah, about 35km to the west, we visit the more extensive but less excavated ruins at al-Baleed, part of the 12th-century trading port of Zafar, which had seen its heyday by the late 15th century. A footpath wends its way through the waist-high ruins of a great mosque, a citadel and houses, before finishing at the excellent Museum of the Frankincense Land, which brings to life not only the trade in the aromatic resin but Oman’s proud seafaring history, too.

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The pretty fishing village of Taqah, the inhabitants of which make their living from catching sardines in winter (the seas are too rough during the summer monsoon season), is another highlight. Set back from the white-sand beach that extends east from Salalah is Taqah’s 19th-century fort, once the residence of the local wali (governor). The beautifully restored building consists of an outer wall with four watchtowers, an inner courtyard shaded by an old date palm and rooms filled with weapons and handicrafts that illustrate everyday life.

We stop at a similarly restored fort in Mirbat, 40km east of Taqah, topped by cannons overlooking another small harbour through which frankincense once passed, and wander streets lined with merchant’s houses that were reduced to rubble during the Dhofar Rebellion.

What began in 1962 as a tribal revolt against the unpopular Sultan Said bin Taimur evolved into a civil war that lasted until 1976, with the rebels supported by communist-run South Yemen and the sultan deposed by his British-backed son, the current Sultan Qaboos bin Said al Said, in a 1970 coup. The town has a second, crumbling fort that was the scene of the 1972 Battle of Mirbat, in which nine British SAS soldiers repelled an attack by 300 communist guerillas.

On the other side of Salalah, towards the Yemen border, the road begins to zigzag 1,000 metres up the Jabal al Qamar, or Moon Mountains, which are as spookily lunar as they sound, especially when enveloped in cloud during the khareef.

Mussallem drives gingerly through a total whiteout to a lookout, where we can barely see our hands in front of our faces. The view is normally spectacular, he assures us, but our disappointment is tempered by the delight of the Arab tourists in the car next to us, who have perhaps never seen thick fog before.

Having headed back into town, slowing for the camels that cruise the motorway, we visit Al-Husn souk, a colourful market with a neat grid of pedestrianised alleyways next to the Sultan’s palace. The souk is brimming with small shops selling frankincense and powdered incense and the shopkeepers are unfailingly friendly. They are not the only ones.

After bidding farewell to Mussallem, we struggle to catch a taxi, before a local pulls up to offer us a lift. I can’t think of many other countries in which we’d accept a ride from a stranger, but it’s normal in these parts.

As we make our way around town in a variety of cars, one jovial Dhofari even insists on buying us fresh coconut juice and frozen chunks of sugar cane from one of Salalah’s many fruit stalls before dropping us off.

We do manage to flag down a taxi to take us to the Salalah Tourism Festival, an annual celebration of Dhofari culture held from mid-July to the end of August. Amid the funfair rides and stalls selling candy floss, we watch barah, a Bedouin dance performed to drums and the chanting of poetry, and alhbot, a routine wherein men line up and sing, and then, one by one, leap in the air, brandishing a sword.

The world may be getting smaller, but Salalah still feels like a distant land.