The houses of Al-Balad, Jeddah's historic quarter, were built of coral stone cut from the Red Sea reefs, and their facades are hung with rawasheen: tall wooden bay windows of carved lattice that let the sea breeze in and kept the sun and the street's gaze out. They are an architecture of air and modesty at once, and they explain a good deal about how women dress in this city. The answer to what to wear in Jeddah for women follows the same logic as those windows: cover, but let the air through.

Historic Jeddah was inscribed as a UNESCO World Heritage Site in 2014, recognised as the old gateway through which pilgrims passed on their way to Mecca. Today its lanes are being restored, and they hold galleries, coffee houses and small museums alongside the old merchant houses. The guidance for visitors is clear and simpler than many expect. Foreign women are not required to wear an abaya or a headscarf, but modest dress is expected in public: shoulders and knees covered, and clothes loose rather than tight.

Within those terms, linen is the obvious cloth. Jeddah is hot and humid for much of the year; even in the cooler months from November to March, daytime temperatures sit around the high twenties and low thirties, and the air off the Red Sea is heavy. The PP linen blouse in Sky Blue covers the arms and falls to a curved hem at the hip; with loose full-length trousers it meets everything the city asks and keeps air moving at the skin. In Orchid, a certified Belgian linen colourway, it reads a little dressier for an afternoon in the galleries of Al-Balad.

Some visitors choose to wear an open abaya over linen, as many Saudi women do, and the combination is comfortable: the abaya worn loose and unfastened, a linen blouse beneath it. Others prefer a shirt worn over trousers. The HER Laos Linen Shirt in Blue or Pink, worn loose and untucked, serves that purpose well, as does the HER Cuba Linen Shirt in Lemon Yellow. All are in the women's linen collection.

The Corniche is where Jeddah walks in the evening. It runs for miles along the Red Sea, past sculpture parks and the jet of King Fahd's Fountain, among the tallest in the world, which rises from the water offshore. Families gather on the waterfront after sunset when the heat eases, and the dress is the same modest register as the old town, a little more relaxed. A blouse in Lemon or Pink with light trousers and flat sandals is entirely right.

The private beach clubs and resorts north of the city, around Obhur and along the coast, keep a different code within their gates, closer to that of any international beach resort. This is where the Amelia linen dress shirt belongs: in Dubarry or Oyster, worn on its own as a dress, for lunch by the pool or an evening at the club. Since it is cut to the thigh, it stays inside the resort rather than going into the city. The ladies linen set in Sky Blue, a blouse with matching shorts, follows the same rule. The same distinction between resort and town holds further north, at the new resorts of the Saudi Red Sea.

Jeddah also has a calendar of its own. The Saudi Arabian Grand Prix runs on the Corniche circuit in the spring, and the city's cultural season fills the restored houses of Al-Balad through the winter. For a broader picture of the region, the women's guide to AlUla covers the desert north-west, where the evenings are cooler and the setting entirely different.

In December the Red Sea International Film Festival brings its premieres and its evening crowds to the coral-stone courtyards of Al-Balad, and the old quarter is lit late into the night.

Read more: What to Wear in Jeddah  ·  The Linen Brand for Jeddah  ·  The Linen Brand for Saudi Arabia