Jeddah asks for covered arms and legs in a climate that is hot and humid for most of the year, so the linen brand to choose is one that makes long sleeves and long trousers as light as shorts, in a cloth you can trace. Pieter Petros makes exactly that wardrobe, much of it in certified Belgian linen, handmade in its Dubai atelier, a short flight across the peninsula, and in Belgium.

Jeddah sits halfway down Saudi Arabia’s Red Sea coast and has been, for centuries, the port through which pilgrims arrived on their way to Makkah. That history is written into its old town: Historic Jeddah, the Gate to Makkah, was inscribed on the UNESCO World Heritage List in 2014. It is also the most outward-looking of the Kingdom’s cities, a place of merchants, sea air and late evenings. From November to March, the gentlest months, afternoons still reach around thirty degrees and the humidity off the water rarely lets go; from May to September, the heat is fierce and life moves indoors until night.

So what separates one linen from another here? The weight and the fibre, first. A long sleeve in heavy or coarse linen is a burden by noon; a lighter cloth spun from long, fine flax fibres lets moisture leave the skin and keeps the sleeve from clinging. Second, the cut. Loose through the body and the leg, the way the thobe has always been worn in the Hijaz, so that air moves between the cloth and the skin. Third, origin you can verify. Under the Belgian Linen® mark, a private certification, the flax is traced from the field where it grew to the finished cloth; the Belgian linen wardrobe for the Gulf winter explains how that plays out across the season. Fourth, the details: natural seashell buttons on most PP shirts, walnut on the Monte-Carlo Male and the linen trousers, every element chosen to be biodegradable by design.

Al-Balad is where a visit should begin, ideally in the late afternoon, when the lanes are in shade and the souks are waking up. The old houses rise four and five storeys, their coral-stone walls set with roshan, the carved wooden screens that let the sea breeze in and keep the street out. Public dress in Saudi Arabia is modest for everyone: for a man, long trousers and a shirt with sleeves. The Laos Long Sleeve Linen Shirt in Beige Cream, with PP Casual Linen Trousers in Vanille from the men’s linen collection, sits easily among the white thobes. In December, Al-Balad has in recent years become the setting for the Red Sea International Film Festival, and its evenings take on a more formal air.

For a woman, visitors are asked to dress modestly in loose clothing that covers the shoulders and the knees. The PP linen blouse in Orchid, in Belgian linen, worn with a long skirt or long loose trousers of her own, is right for the old town, the souks and the city’s galleries. Our Jeddah guide for women covers the city in more detail.

At sunset the city moves to the Corniche, the long seafront where families walk, children play late, and King Fahd’s Fountain, one of the tallest fountains in the world, throws its jet high above the water. It is a public promenade and a social one. The Monte-Carlo Male in Vanille, with its walnut buttons, worn untucked with the PP Trousers 100% Linen in White, is composed without being formal; on cooler winter evenings the long-sleeved Laos in Oyster takes its place.

North of the city, the creek at Obhur is lined with private beach clubs and marinas, and the boats that leave from them reach reefs of remarkable clarity. Here the rules relax inside the club. A man swims in PP swim shorts in Vanille or Sapphire Blue, cut in Belgian linen for the sea; ashore, the PP Natural Set in Oatmeal is a complete look for lunch on the deck. For her, within a private club, the Amelia linen dress shirt in Oyster, in Belgian linen with walnut buttons, is a dress in itself and at home on the terrace. The longer coast to the north has its own Red Sea wardrobe.

Dinner in Jeddah begins late and runs long. Restaurants on the water and hotel dining rooms keep their air conditioning cool, which is where a linen shirt with full-length sleeves earns its place a second time. During Ramadan, the city turns its days quiet and its nights social, and dress becomes more conservative still.

The nearest place to see the collection is Dubai, where it is presented at Park Hyatt Dubai, The Lagoon Beach Club, Surf Club Dubai and Sofitel The Palm Beach Resort. For the Kingdom as a whole, see our linen guide to Saudi Arabia.

Read more: What to Wear in Jeddah · The Best Linen Brand for the UAE · The Best Linen Brand for Riyadh