Saudi Arabia
Saudi Arabia Geography & Climate
Geography
Saudi Arabia covers roughly 2.15 million square kilometres, some four-fifths of the Arabian Peninsula, and it has no permanent rivers or lakes at all — the largest country in the world of which that is true.
The Empty Quarter
The Rub al Khali fills the south and south-east: about 650,000 square kilometres of sand, the largest continuous sand desert on earth, with dunes reaching 250 metres and areas that go years without measurable rain.
The Nafud and the interior
The Great Nafud in the north is a red sand sea; between the two runs the Dahna, a narrow arc of dunes. Between them lies the Najd plateau, the rocky heartland where Riyadh sits, cut by the Tuwaiq escarpment — the cliff edge known as the Edge of the World.
The west
The land rises from the Red Sea to the Hejaz and Asir mountains, which reach above 3,000 metres in the far south-west. Asir catches monsoon moisture, is terraced and wooded, and is nothing like the rest of the country. This is also volcanic ground — the harrat lava fields around Medina and Khaybar are vast.
The east
A low limestone plain running to the Gulf, holding the world’s largest conventional oil reserves and, at Al-Ahsa, the largest oasis on earth, fed by artesian springs.
A desert that was not always one
The peninsula has swung between wet and dry over tens of thousands of years, and the evidence is everywhere once you know to look: fossil lake beds in the Nafud, thousands of stone structures on the lava fields that predate the pyramids, and rock art at Jubbah and Shuwaymis — UNESCO-listed — showing cattle, ostriches and hunting scenes in country that now supports none of it.
Water
Almost all drinking water is desalinated, and the fossil aquifers used for agriculture are being drawn down faster than they can ever refill.
Climate Patterns
Saudi Arabia is overwhelmingly arid, and the practical consequence for a visitor is simple: the country is comfortable for about five months of the year and hostile for the rest.
Summer
From May to September the interior runs 42 to 48°C by day, and the Empty Quarter and the Eastern Province go higher. Jeddah and the Red Sea coast are the hardest, because humidity is added to the heat, and nights stay near 30°C. Outdoor work is banned during the middle of the day in the hottest months.
Winter
November to March is pleasant: 20 to 28°C by day in Riyadh and AlUla. Desert nights are the surprise — clear skies and dry air let the heat go completely, and the interior can fall to near freezing. A desert camp in January needs a proper coat, which visitors routinely fail to bring.
Rain
Under 100 millimetres a year across most of the country, and in parts of the Empty Quarter effectively none. What does fall often arrives as a sudden downpour, and flash floods in normally dry wadis are a genuine and regular hazard, killing people most years.
Asir
The exception. Above 2,000 metres in the south-west, Abha catches the tail of the Indian Ocean monsoon between June and September, stays around 20°C, and is misty and green — which is why Saudis holiday there in summer.
What it means for planning
The upshot is that the season chooses the trip rather than the other way round. AlUla, Riyadh, the Empty Quarter and Diriyah are winter destinations and genuinely unpleasant outside that window; the Red Sea is divable year round but brutal on land in summer; and Asir inverts the whole pattern by being at its best in the months everywhere else is impossible. A summer visit that ignores this tends to become a tour of shopping malls.
Dust
Sandstorms are common in spring, cutting visibility, closing airports and lasting days.